JUt- 


Bulletin  No.  1 January  1911 

Second  edition  January  1912 

Oregon  State  Bureau  of  Mines 

HENRY  M.  PARKS 

DIRECTOR 


ROAD  MATERIALS 

IN  THE 

WILLAMETTE  VALLEY 


The  bulletins  of  the  Bureau  of  Mines  are  sent  free  to  all  residents 
of  Oregon  who  request  them. 


Series  1]  Entered  as  second-class  matter  November  27,  1909,  at  the  postoffice  [No.  46 
at  Corvallis,  Oregon,  under  the  act  of  July  16,  1894. 


UNIVERSITY  OF 
ILLINOIS  LIBRARY 

AT  URBANA-  CHAMPAIGN 


m 2 2 >531 


Reconnaissance  Map 

of  the 

Willamette  Valley 

Showing  available  outcrops  of  road 
materials  in  the  more  densely 
populated  portion. 


Road  Materials  the  Willamette  Valley 


OREGON  AGRICULTURAL  COLLEGE  PRESS 


CONTENTS, 


\*\  \ ^ 


Introduction. 

General  geology  of  the  Willamette  Valley. 

Physical  properties  of  rock-making  minerals. 

Rock  classification. 

Igneous  rocks — 

Structure. 

Mineral  content. 

Corelation  of  mineral  content  and  structure  with  physical  prop- 
erties. 

Comparative  value  for  road  materials. 

Sedimentary — 

Structures. 

Comparative  value  for  road  materials. 

Metemorphic — 

Structure. 

Comparative  value  for  road  materials. 

Rock  weathering  and  its  effect  from  standpoint  of  road  material. 
Description  of  laboratory  test. 

Discussion  of  the  value  of  laboratory  tests. 

Road  material  situation  by  counties — 

Benton. 

Clackamas. 

Lane. 

Linn. 

Marion. 

Multnomah. 

Polk. 

Tillamook. 

Washington. 

Yamhill. 

Suggestions  for  selecting  quarry  sites. 

Gravels  in  the  Willamette  river. 

General  Observations. 

Cost  data. 

Summary  and  conclusion. 


Plate  i. — Graphic  Granite.  Note  the  parallel  arrangement  of  the  quartz  and  feldspar  crystals 


5 

INTRODUCTION, 


It  has  often  been  stated  that  Oregon  has  more  good  road  material  than 
any  other  state,  a statement  which  is  doubtless  true.  The  fact  still  re- 
mains, however,  that  the  road  builders  of  our  state  are  usually  not  suf- 
ficiently well  versed  in  principles  of  geology  to  be  able  to  distinguish 
excellent  material  from  that  of  medium  quality,  nor  the  material  of  me- 
dium quality  from  the  poor  material.  It  is  also  a fact  that  the  road 
builder  will  often  transport  his  material  for  long  distances  at  an  extra 
cost  when  as  good  or  better  material  is  close  at  hand. 

The  main  purpose  of  this  bulletin  is  to  set  forth  in  plain  language  the 
fundamentals  of  geology  as  they  apply  to  the  principles  of  scientific 
road  building  so  that  the  road  builder,  by  appropriating  these  principles, 
will  be  able  very  largely  to  pass  judgment  without  having  to  be  at  the 
mercy  of  another’s  opinion  or  judgment. 

This  bulletin  is  not  intended  to  be  a scientific  treatise  in  geology,  but 
is  written  expressly  for  the  road  builder,  using  only  the  principles  of 
geology  in  so  far  as  they  can  be  applied  to  the  intelligent  selection  an  1 
handling  of  road  materials. 

The  field  observations  which  form  the  basis  of  this  report  were  made 
by  H.  M.  Parks,  assisted  by  S.  W.  French  and  H.  E.  Cooke,  and  was  com- 
pleted during  the  summer  vacation  months  of  July,  August  and  Septem- 
ber of  1910.  The  area  covered  in  this  reconnaissance  includes  only  the 
more  densely  populated  portion  of  the  Willamette  Valley,  which  is  in 
general  the  main  floor  of  the  valley,  including  only  the  first  rim  of 
foothills  as  a boundary. 

It  was  thought  that  a more  extensive  survey  far  back  Into  the  tributary 
valleys  and  foothills  is  not  warranted  at  this  time  for  three  reasons- 
First,  because  it  was  found  that  these  ultra  rural  communities  are  sup- 
plied with  good  outcrops  in  much  greater  quantities  than  the  valley 
proper;  and,  second,  because  of  greater  immediate  demand  for  road 
materials  in  the  central  valley;  and,  third,  because  of  lack  of  funds  anl 
time  for  carrying  on  the  work.  More  than  five  hundred  different  out- 
crops were  examined  in  the  area  indicated,  average  types  of  these  were 
selected  and  sent  in  to  the  college  for  more  detailed  examination. 

The  map  accompanying  this  bulletin  is  not  intended  as  a geological 
map  and  does  not  show  all  the  outcrops  of  rock  in  the  area  covered,  but 
it  is  intended  to  show  only  the  approximate  areas  in  which  available  out 
crops  of  good  road  materials  are  found,  as  well  as  indicating  the  ones 
to  be  shunned.  The  map  will  be  very  serviceable  in  showing  the  general 
distribution  of  available  materials,  not  only  in  the  valley  as  a whole,  but 
in  each  county  or  locality.  Owing  to  the  inaccuracy  of  any  available  base 
maps  of  the  area  treated,  it  was  found  impossible  to  locate  these  out- 
crops with  extreme  accuracy.  For  this  reason,  after  the  approximate 
location  is  determined,  the  reader  should  depend  upon  the  locality  de- 
scription for  more  accurate  information.  This  will  be  found  under  Road 
Material  Situation  by  Counties. 


6 


We  wish  to  acknowledge  our  appreciation  for  the  courtesies  shown  by 
the  railroad  companies  of  the  valley  in  furnishing  transportation  by  tho 
different  county  courts,  which  aided  materially  in  defraying  local  ex- 
penses; by  the  Oregon  Good  Roads  association  in  assisting  in  creating 
favorable  sentiment  toward  the  carrying  out  of  this  work,  and  by  M.  O. 
Eldridge  of  the  Department  of  Good  Roads,  Washington,  D.  C.,  for  photo- 
graphs, as  well  as  others  who  furnished  illustrative  material.  We  also 
wish  to  express  our  appreciation  for  the  faithful  work  of  Messrs.  S.  H. 
Graf,  P.  A.  Jones  and  M.  A.  Nickerson  in  making  laboratory  tests. 

GENERAL  GEOLOGY  OF  THE  WILLAMETTE  TALLEY. 

A few  of  the  general  principles  of  geology  as  applied  to  the  Willamette 
Valley  will  not  be  out  of  place,  and  may  be  of  some  service  in  the 
interpretation  of  the  material  which  follows  in  this  bulletin,  as  well  as 
accounting  for  some  of  the  more  important  surface  features,  such  as 
topography,  general  character  of  soils,  etc. 

The  main  trough  of  the  Willamette  Valley  is  a structural  valley;  that, 
is,  it  was  formed  originally  by  mountain  making  foldings  approximately 
parallel  to  each  other  on  either  side,  having  the  valley  proper  as  a 
trough  between  the  two  folds.  These  folds  were  exaggerated  at  the 
same  time  and  also  later  by  the  addition  of  a large  amount  of  volcanic 
material  poured  out  from  numerous  volcanoes  distributed  along  each  of 
the  folds.  The  first  of  these  two  folds  to  appear  above  the  ocean  level 
was  the  Cascades  on  the  east  of  the  valley.  They  were  developed  during 
the  Eocence  period,  and  during  this  period,  as  well  as  a large  part  of 
the  Miocene  period  which  followed,  formed  the  Pacific  Coast,  or  in  other 
words,  formed  the  western  border  of  the  continent  at  this  latitude  during 
that  time.  During  the  Miocene  period  the  coast  range  was  pushed  up 
from  the  sea  floor  on  the  west  of  the  valley,  but  was  not  fully  developed 
until  the  Pliocene  period  which  followed.  Still  later  during  the  Pleis- 
tocene period  the  Willamette  Valley  was  a bay  or  sound  similar  to  the 
Puget  Sound  of  today.  A considerable  amount  of  fine  sediment  was 
washed  from  these  hills  during  this  time  and  distributed  over  the  floor 
of  the  bay.  This  is  probably  the  principal  source  of  our  deep  heavy 
clay  soils  so  general  over  the  main  floor  of  the  valley. 

During  the  time  since  these  two  mountain  ranges  have  appeared  above 
the  ocean,  until  the  present  time  the  weathering  agencies  such  as  frost, 
wind,  rain,  etc.,  have  been  hard  at  work  upon  them,  wearing,  rotting 
and  carrying  them  away  and  we  find  them  today  ramified  by  a network 
of  streams  which  have  carved  deep  canyons  upon  their  slopes  and  in 
that  way  exaggerating  to  a large  extent  the  ruggedness  of  the  original 
topography  of  these  mountain  slopes.  In  as  far  as  the  agencies  of 
decay  such  as  ground  water,  frost,  etc.,  have  been  able  to  keep  in 
advance  of  the  transporting  agencies  such  as  running  water,  wind,  etc  . 
just  that  far  has  the  soil  been  able  to  accumulate  upon  these  hillsides. 
Whenever  the  transporting  agencies  are  able  to  keep  pace  with  the 
decaying  agencies  of  the  rocks,  there  we  find  the  rocks  bare  or  as  we 


7 


say,  outcropping.  On  this  account  the  southwest  slopes  of  our  hills  in 
the  Willamette  Valley  have  thinner  soils  and  more  outcrops  than  the 
northwest  slopes.  This  is  due  to  the  prevailing  winds  from  the  south 
west  and  in  a great  many  cases  the  soils  are  carried  away  as  fast  as 
formed.  Again  we  find  outcrops  almost  universally  upon  the  steep 
slopes  of  stream  canyons,  where  the  soil  is  carried  away  as  fast  as 
formed. 

The  Willamette  Valley  is  most  fortunate  in  having  a goodly  supply  of 
rocks,  which  are  exceptionally  well  adapted  for  road  materials,  as 
well  as  being  well  distributed  over  the  valley.  We  have  already  seen 
that  these  mountain  ranges  on  either  side  of  the  valley  are  largely 
composed  of  volcanic  material.  These  volcanic  materials  are  very 
largely  basic  lavas  and  form  the  class  of  rocks  which  are  usually  known 
to  the  road  builder  as  “trap”  or  “trap  rock”.  From  a petrographic  stand- 
point they  form  the  basalts  and  diabases.  As  will  be  seen  later  these 
rocks  as  a class,  from  the  standpoint  of  road  materials,  are  as  good  as 
the  best.  A large  part  of  these  trap  rocks  are  surface  lava  flows  whil^ 
some  are  found  as  dikes  or  intruded  sheets.  These  rocks  are  found 
mostly  in  the  foot  hills  where  they  have  been  exposed  by  erosion,  thus 
making  a more  or  less  continuous  rim  around  the  main  floor  of  the 
valley.  Aside  from  this  rim  or  boundary  of  outcrops,  we  find  numerous 
buttes  scattered  promiscuously  over  the  valley,  nearly  all  of  which  are  of 
volcanic  origin  and  are  composed  of  basalt.  As  types  of  these  might  be 
mentioned  Knox  and  Peterson  Butte  in  Linn  county,  Skinner’s  and 
Gillespie  Buttes  in  Lane  county  or  Kelley  and  Rocky  Butte  in  Multnomah 
county.  Some  of  these  buttes  have  a certain  amount  of  sedimentary 
rocks  in  places  on  the  surface,  but  the  main  mass  is  basalt. 

PHYSICAL  PROPERTIES  OF  ROCKMAKING  MINERALS. 

It  is  evident  at  the  outset  that  the  physical  properties  of  rocks  will 
be  dependent  to  a large  extent,  upon  the  physical  properties  of  the  most 
important  minerals  of  which  they  are  composed,  size,  and  shape  of  its 
constituent  mineral  grains.  Fortunately  the  number  of  important  rock 
making  minerals  are  few  and  in  the  discussion  of  these,  we  will  attempt 
to  group  them  as  far  as  possible,  putting  those  with  similar  physical 
characteristics  in  a group. 

Probably  the  most  important  of  all  rock  forming  minerals  is  Quartz. 
Its  composition  is  pure  silica.  It  is  the  hardest  of  all  rock  making 
minerals  which  we  will  discuss.  It  is  a comparatively  tough  mineral  on 
account  of  having  no  cleavage;  that  is,  it  has  no  tendency  to  break  in 
one  direction  more  than  in  another.  As  a result  it  has  a glass  like 
fracture  and  breaks  in  curves  instead  of  in  planes.  Quartz  is  very 
widely  distributed  in  nature  occurring  more  or  less  in  nearly  all  rocks 
except  the  basic  igneous  ones,  but  from  a road  material  standpoint  it 
is  most  important  in  the  acid  igneous  rocks  and  sandstones.  From  the 
standpoint  of  toughness  and  hardness  it  is  probably  the  best  rock 
forming  mineral  known.  What  better  recommendation  as  a road  material 


8 


mineral  could  be  asked  than  the  fact  that  we  find  it  the  most  resistant 
mineral  in  nature’s  abrasion  test,  as  is  evidenced  by  the  large  amount 
of  it  found  in  the  sand  on  the  sea  beach,  it  being  almost  the  only  one 
which  is  able  to  survive  the  severe  grinding  action  of  the  waves. 

The  Feldspars  are  probably  the  next  in  importance  as  rock  making 
minerals.  We  will  discuss  these  as  a group  because  of  their  like 
characteristics.  They  are  somewhat  inferior  in  hardness  to  quartz,  about 
the  same  in  hardness  as  the  pen  knife.  All  of  the  feldspars  are 
comparatively  brittle.  This,  to  a large  extent,  is  due  to  the  fact  thst 
these  minerals  have  a natural  cleavage  in  two  directions  at  right  angles 
to  each  other  or  nearly  so,  which  means  that  each  crystal  of  feldspar 


Pirate  2. — “Boulders  of  weathering,”  showing  how  round  boulders  are 
formed  from  angular  blocks. 

no  matter  how  tiny,  has  two  directions  of  easy  breaking  at  every 
microscopic  point  in  its  mass.  On  this  account  they  will  be  more  easily 
broken  up  under  impact  or  abrasion  than  they  would  otherwise  be. 
Another  reason  which  makes  for  easy  breaking  in  the  feldspars  is  that 
one  of  its  directions  of  cleavage  or  easy  breaking  is  at  right  angles  to 
the  long  direction  of  the  crystal,  making  an  easy  breaking  plane  in  the 
direction  of  greatest  stress.  The  feldspars  are  found  in  most  of  the 
igneous  rocks  but  occur  in  large  proportions  in  the  more  acid  ones. 

The  Pyroxenes  and  Amphiboles  are  two  classes  or  groups  of  minerals 
which  are  so  nearly  alike  in  their  physical  characteristics  that  they  will 
be  discussed  in  this  connection  under  one  head.  They  have  about  the 
same  hardness  as  the  feldspars,  are  dark  in  color,  usually  dark  green 
black  or  brown.  These  minerals  are  found  in  nearly  all  igneous  rocks 
but  are  more  plentiful  in  the  more  basic,  dark  colored  ones.  In  fact 


9 


the  dark  color  of  the  more  basic  igneous  rocks  is  due  largely  to  the 
presence  of  these  minerals  in  large  amounts.  They  also  occur  in 
schists.  These  minerals  have  two  directions  of  cleavage,  the  pyroxenes 
at  about  90  degrees  and  the  amphiboles  at  about  125  degrees.  However 
since  their  cleavage  directions  are  parallel  to  the  long  direction  of  their 
crystals  they  resist  breaking  and  are  tougher  than  the  feldspars. 

The  Mica  group  is  of  considerable  importance  as  a rock  making  min- 
eral, occuring  to  a greater  or  less  extent  in  all  the  igneous  rocks,  and  it 
becomes  most  important  in  a large  number  of  metamophic  rocks 
Mica  is  a soft  mineral,  being  only  a little  harder  than  the  finger  nail,  it 
has  a very  perfect  cleavage  in  one  direction.  Although  the  cleavage  flakes 
are  very  tough  and  elastic,  this  property  is  more  than  offset  by  the  easy 
cleavage  and  soft  nature  of  the  mineral.  On  the  whole  the  micas  would 
tend  to  be  a detriment  in  any  rock,  considered  from  the  sandpoint  of  road 
material,  causing  the  rock  to  be  inferior  in  toughness  and  wearing  quali- 
ties. 

Calcite  and  Dolomite  as  primary  minerals  are  the  principal  constituents 
of  all  limestones  and  marbles,  and  occur  sometimes  as  the  cementing 
material  between  the  sand  grains  of  a sandstone.  These  minerals  are 
but  little  harder  than  the  micas.  Because  of  their  soft  nature,  as  well  as 
because  of  the  fact  that  their  cleavage  is  in  three  directions,  at  angles 
of  105  degrees  to  each  other,  they  are  very  brittle  and  friable.  Conse- 
quently they  do  not  possess  physical  characteristics  which  would  recom- 
mend them  as  road  materials. 

Secondary  Minerals,  including  such  minerals  as  kaolin,  chlorite  calcite, 
serpentine,  talc  and  limonite,  may  in  this  discussion  be  included  to  ad- 
vantage in  one  group.  Secondary  minerals  are  those  which  result  from 
the  alteration  of  previously  existing  minerals  by  weathering  or  other 
alteration  agencies.  In  general,  they  are  soft  friable  minerals  whicu 
crumble  easily  under  impact  or  abrasion.  These  minerals  cannot  be  ad- 
vantageous in  any  road  material  except  as  they  assist  in  the  binding  or 
cementing  quality  of  the  rock  in  which  they  occur.  The  soft  and  friable 
nature  of  all  weathered  rocks  as  compared  with  their  respective  fresh 
unaltered  ones,  is  very  largely  due  to  the  presence  of  these  secondary 
minerals.  The  only  exception  to  this  general  rule  would  be  in  the  case 
of  a few  deep-seated  alteration  products  or  secondary  minerals,  such  as 
hornblende,  which  might  increase  the  rock’s  toughness. 

The  following  is  a brief  classification  of  rocks  generally  accepted  by 
all  geologists: 

I.  Igneous — 

1.  Intrusive  (plutonic). 

a.  Granite. 

b.  Syenite. 

c.  Diorite. 

d.  Gabbro. 

2.  Extrusive  (volcanic). 

a.  Rhylite. 


1-2 


10 


b.  Trachyte. 

c.  Andesite. 

d.  Basalt  and  diabase. 

II.  Sedimentary — 

1,  Calcareous. 

a.  Limestone. 

2.  Siliceous. 

b.  Conglomerate. 

c.  Sandstone. 

d.  Chert  (flint). 

III.  Metamorpliic — 

1.  Foliated. 

a.  Gneiss. 

b.  Schist. 

2.  Nonfoliated. 

a.  Slate. 

b.  Quartzite. 

c.  Marble. 

In  order  to  discuss  the  physical  properties  of  rocks  as  to  their  struc- 
(v  •'  rr  ngement  of  their  respective  minerals,  it  will  be  necessary  r.o 
give  a brief  classification  of  rocks  in  general  and  enter  to  some  extent 
into  their  respective  modes  of  origin. 

According  to  their  mode  of  origin  and  the  position  of  the  masses  with 
respect  to  the  earth’s  crust  and  with  each  other,  rocks  naturally  divide 
themselves  into  three  main  groups,  divisions  which  are  recognized  by 
practically  all  geologists.  These  are  Igneous  rocks  made  by  the  solidifi- 
cation of  molten  materials;  the  Sedimentary  or  bedded  rocks  formed  by 
the  precipitation  of  sediments  in  water,  as  well  as  the  aeolian,  or  win  ! 
formed  deposits,  and  the  Metamorpliic  rocks,  those  produced  by  the  sec- 
ondary action  of  certain  geologic  processes  upon  other  igneous  or  sedi- 
mentary rocks  by  which  their  original  characters  are  wholly  or  partly 
obscured  and  replaced  by  new  ones. 

IGNEOUS  ROCKS. 

The  igneous  rocks  are  classified  both  from  the  standpoint  of  their 
structure  and  mineral  content.  We  will  take  up  first  the  most  important 
phases  of  their  structure  because  this  is  an  important  factor  in  the  dis- 
cussion of  their  wearing  qualities. 

STRUCTURE  OF  INGEOUS  ROCKS. 

Most  igneous  rocks  are  made  up  of  interlocking  crystals  of  different 
minerals.  These  crystals  may  be  so  small  that  they  cannot  be  readily 
distinguished  by  the  eye,  or  they  may  be  large  and  easily  seen,  or  some 
may  be  large  and  some  small.  If  they  are  large  enough  to  be  distinct  to 
the  unaided  eye  they  are  termed  coarsely  crystalline  or  coarse  grained. 
Some  igneous  rocks  look  like  glass.  In  fact  they  are  glass,  and  like 
manufactured  glass  they  have  solidified  from  a liquid  so  suddenly  that 


the  crystals  have  not  Imu  a^e  to  6iow.  Such  rock  is  termed  volcanic 
glass  or  obsidian.  Some  igneous  rock  is  made  up  partly  of  glass  and 
partly  of  crystals,  and  between  the  rock,  which  is  wholly  glass,  and  that 
which  is  wholly  crystalline,  there  are  all  gradations  depending  upon  che 
conditions  under  which  it  solidified.  All  liquid  lava  contains  the  materials 
from  which  crystals  may  be  formed  under  proper  conditions.  Volcanic 
rocks  composed  largely  of  glass  may  be  either  very  compact  or  porous. 
Porous  rock  is  really  a sort  of  solidified  lava  froth  and  the  pore  spaces 
in  the  rock  are  the  spaces  occupied  by  gases  when  the  lava  hardened. 

Pumice  contains  the  same  material  as  obsidian,  one  being  porous  and 
the  other  compact.  Scoria  or  Cellular  basalt  is  the  same  material  as 
dense  besalt,  one  being  porous  while  the  other  is  compact. 

All  igneous  rocks  are  supposed  to  have  solidified  from  a molten  mass. 
There  are  a number  of  factors  which  influence  the  structure  or  grain  of 
igneous  rocks,  but  probably  the  most  important  are  rate  of  cooling  and 
pressure.  If  the  molten  mass  is  under  great  pressure  and  a long  time 
is  involved  in  making  the  change  from  the  liquid  to  the  solid  state,  the 
rock  will  be  coarse  grained;  that  is,  made  up  of  large  crystals;  conse- 
quently, the  rocks  which  solidify  deep  down  in  the  crust  of  the  earth  are 
coarse  grained.  If  on  the  other  hand  the  molten  mass  is  suddenly  chilled 
and  under  little  pressure,  we  find  the  resultant  rocks  are  glasses  or  else 
dense  or  microscopically  fine  grained;  these  rocks  we  find  usually  as  the 
lavas  which  are  forced  out  upon  the  surface  of  the  earth.  Sometimes 
these  molten  lavas  do  not  reach  the  surface  of  the  earth  but  are  thrust 
into  or  between  layers  of  the  crust  of  the  earth  and  cooled  under  moderate 
pressure  and  with  moderate  rapidity.  We  would  therefore  expect  to  find 
them  and  do  usually  find  them  intermediate  in  grain,  or  structure,  al- 
though we  sometimes  find  them  dense  and  fine  grained  and  sometimes 
rather  coarse  grained. 

MINERAL  CONTENT  OF  IGNEOUS  ROCKS. 

Igneous  rocks  are  also  classified  according  to  their  mineral  content, 
and  as  we  have  already  found  that  the  different  rock  making  minerals 
vary  widely  in  the  physical  properties  which  affect  their  wear,  it  will  be 
necessary  to  get  in  mind  the  main  differences  in  the  mineral  make-up  of 
igneous  rocks. 

The  following  table  will  give  an  approximate  idea  as  to  the  amount  of 
the  different  rock  making  minerals  in  each  of  the  common  types  of  igneous 
rocks: 


Coarse  grained.  Feldspars  Quartz  Amphiboles  & Pyroxene  Mica 


Per  cent 

Per  cent 

Per  cent 

Per  cent 

Granite  

50-60 

25-35 

0-15 

5-15 

Syenite  

60-30 

0-  5 

0-15 

5-15 

Diorite  

30-50 

0-10 

25-40 

5-10 

Gabbro  

25-45 

0 

30-50 

5-10 

Rhyolite  

40-55 

10-20 

0-  5 

5-10 

Andr-dte  

35-55 

0 

5-20 

5-10 

12 

CORELATION  OF  MINERAL  CONTENT  AND  STRUCTURE  WITH 
PHYSICAL  PROPERTIES. 


Continuing  the  discussion  of  igneous  rocks,  we  find  the  texture  and 
size  of  the  crystals  have  an  important  bearing  upon  the  resistance  to 
wear.  All  other  factors  being  equal,  a coarse  grained  rock  will  give  a 
higher  percentage  of  wear  than  a fine  grained  rock.  This  is  as  would 
be  expected  from  a petrographic  standpoint,  and  can  be  explained 
largely  from  the  standpoint  of  cleavage.  Since  in  all  the  igneous  rocks 
a large  proportion  of  its  minerals  or  crystals  have  easy  directions  of 
breaking,  if  the  crystal  be  large  a much  larger  volume  of  the  rock  will 
be  involved  in  the  break  than  if  the  crystal  be  small.  We  find  then,  as 
we  would  expect,  that  a coarse  grained  granite  will  give  a greater 
percentage  of  wear  than  a fine  grained  granite,  and  a coarse  grained 


Pl,aTE  3. — Section  through  basalt  “boulder  of  weathering,”  showing 
weathered  effect  close  to  the  surface,  hard  fresh  rock  in  the  center. 

gabbro  will  give  a higher  percentage  of  wear  than  a fine  grained  diabase. 

A gain,  we  found  in  the  description  of  some  of  the  important  minerals 
of  igneous  rocks  that  the  feldspars  have  one  of  its  cleavage  directions 
about  at  right  angles  to  the  long  direction  of  its  crystal  while  in  the 
case  of  hornblende  and  pyroxene  their  cleavages  are  parallel  to  the 
long  direction  of  the  crystal.  A simple  illustration  will  make  the  point 
clear.  Consider  two  heaps  of  wrooden  blocks  all  of  the  same  dimensions 
and  being  two  or  three  times  as  long  as  their  width  and  thickness.  The 
first  heap  are  all  sawed  so  that  the  grain  of  the  wood  is  at  right  angles 
to  the  long  direction  of  the  block  while  the  second  heap  are  all  sawed 


13 


so  that  the  grain  is  parallel  to  the  long  direction.  Now  cement  each 
heap  together  with  some  strong  cementing  substance  so  that  its  respective 
blocks  will  be  mutually  interlocking  in  every  conceivable  direction.  It 
is  very  evident  that  if  we  compare  our  two  “made  to  order”  rocks  either 
from  the  standpoint  of  abrasion  or  from  impact  that  “crossgramite”  will 
be  much  inferior  in  wearing  qualities  to  “straight  graimte”.  Applying 
this  principle  then  to  our  igneous  rocks  of  equal  size  grain,  whether 
coarse  or  fine,  we  would  expect  to  find  that  the  basic  igneous  rocks  which 
have  a higher  percentage  of  hornblende  and  pyroxene  and  less  feldspars 
would  hold  together  and  withstand  abrasion  better  than  the  acid  igneous 
rocks,  which  have  a higher  percentage  of  feldspar  and  are  low  in  pyroxene 
and  hornblende.  Also,  that  the  acid  rocks  would  be  more  brittle  and 
friable  and  less  desirable  for  road  material  than  the  basic  rocks.  This 
is  as  we  find  it  and  is  probably  the  most  logical  reason  why  coarse 
grained  gabbros  and  diorites  give  better  results  than  the  granites  or 
syenites  with  the  same  size  srystals.  The  same  reasoning  would  apply 
in  comparing  the  rhyolites  or  trachytes  with  the  basalts. 

In  order  to  further  illustrate  this  principle  of  cleavage  of  minerals  in 
its  effect  upon  the  durability  of  road  materials  let  us  consider  a certain 
special  type  of  granite  which  is  called  “graphic  granite”.  This  rock  is 
without  doubt  the  most  brittle  and  friable  of  all  unaltered  igneous  rocks, 
and  the  most  skeptical  will  be  convinced  upon  careful  observation  that 
its  brittle  and  crumbly  nature  is  very  largely  due  to  the  arrangement  of 
its  crystals,  and  the  cleavage  of  the  feldspar  which  composes  probably 
two-thirds  or  three-fourths  of  its  mass.  By  referring  to  Fig.  1 the 
leader  will  see  that  this  rock  has  a peculiar  structure  in  that  it  is 
made  up  almost  entirely  of  two  minerals,  feldspar  and  quartz,  and  that 
the  crystals  of  quartz  and  feldspar  are  very  long  and  narrow,  as  well 
as  parallel  to  each  other.  A further  peculiarity  of  the  structure  of  the 
rock  is  that  the  feldspar  crystals  are  very  large,  in  fact  the  specimen 
illustrated  in  Fig.  1 is  only  a part  of  a large  crystal  of  feldspar  enclosing 
within  its  mass  a large  number  of  smaller  quartz  crystals.  It  also 
happens  that  the  two  cleavage  directions  of  the  feldspar  crystal  at 
right  angles  to  each  other  are  both  parallel  to  these  long,  slim,  quartz 
crystals  enclosed  in  the  feldspar.  This  being  the  case  these  easy  break 
ing  planes  pass  between  the  quartz  crystals  and  the  rock  naturally 
breaks  between  the  quartz  masses  for  long  distances,  scarcely  rupturing 
them  at  all.  For  this  reason  a large  mass  of  graphic  granite  can  be 
easily  broken  with  a tack  hammer  while  the  mass  of  ordinary  granite 
composed  of  the  same  minerals  in  equal  amounts,  but  whose  crystals 
are  interlocked  in  every  conceivable  direction  would  be  very  lard  to 
break  even  with  a 4-pound  hammer. 

In  comparing  the  different  types  of  igneous  rocks  as  to  their  adapta- 
bility for  road  material,  we  have  already  found  that  in  general  the  fine 
grained  rocks  are  superior  to  the  course  grained  in  wearing  qualities. 
From  this  standpoint  the  rhyolites,  trachytes,  andesites  and  basalts 


14 

would  be  superior  to  their  coarse  grained  equivalents,  granites,  syenites, 
tiiorites  and  gabbros. 

Again  from  the  standpoint  of  mineral  content  we  have  found  that 
rocks  which  contain  a large  amount  of  the  tough  minerals,  hornblende 
or  pyroxene,  at  the  expense  of  the  more  brittle  and  friable  feldspars 
are  superior  in  toughness  and  wearing  qualities.  For  this  reason  we 
find  the  diabases  and  basalts  will,  in  general,  give  better  results  than 
the  equally  fine  grained  rhyolites  and  trachytes.  The  former  are  rich 
in  hornblende  and  pyroxene  with  a comparatively  small  amount  of 
feldspar,  while  the  latter  have  a very  large  percentage  of  feldspars  and 
a small  percentage  of  pyroxene  and  hornblende.  For  this  same  reason 
granites  and  syenites  which  are  made  up  of  a high  percentage  of 
feldspars  will  be  found  inferior  in  general  to  the  equally  coarse  grained 
diorites  and  gabbros  whose  mineral  constituents  are  made  up  of  a 
higher  percentage  of  pyroxene  and  hornblende.  By  reference  to  the 
accompanying  table  which  was  compiled  from  a table  in  Bulletin  No.  31 
Office  of  Public  Roads,  U.  S.  Department  of  Agriculture,  page  14,  these 
principles  are  further  illustrated: 


Table  Showing  Corelation  of  Mineral  Content  with  the  Physical 
Properties  of  Igneous  Rocks. 


ROCK  VARIETIES 

Mineral 

£> 

d 

p 

•-j 

N* 

Compositi 

percem 

<D 

& 

to 

•d 

P 

*-s 

to 

on  exp res 
tage. 

hd 

B ^ 

« E2  o 

8 

l S 

CD  » 

TO 

sed  in 

g 

o 

P 

Percentage 
of  wear 

Toughness. . . 

Granite  

31. 

66.8 

8.1 

3.5 

15 

Biotite  Granite  

28. 

52.7 

1.9 

11.3 

4,4 

10 

Hornblende  Granite 

24.9 

50.7 

14.9 

5.9 

2,6 

21 

Augite  Syenite  

4.3 

74.7 

8.6 

4.2 

2.6 

10 

Diorite  

6,2 

36.8 

34.1 

4.2 

2.9 

21 

Augite  Diorite 

1.1 

51.6 

28.1 

8.9 

2.8 

19 

Cabbro  

.7 

42,7 

38.9 

4.9 

2.8 

16 

Rhyolite  

38. 

45.2 

1.2 

5.1 

3.7 

20 

Andesite 

12.7 

45.7 

10.5 

7.9 

4.7 

11 

Fresh  Basalt  

8.2 

36.1 

45.1 

.3 

3.3 

23 

Altered  Basalt 

10.3 

28.6 

24.9 

10.2 

5.3 

17 

Fresh  Diabase  

48.8 

44.4 

1.3 

2. 

30 

Altered  Diabase  .... 

.6 

37.4 

27.7 

14.3 

2.5 

24 

The  data  given  in  this  table  shows  the  average  results  on  a large 
number  of  rocks  of  each  type  and  shows  very  satisfactorily  the  relation 


15 


between  the  laboratory  tests  for  physical  properties  and  mineral  con- 
tent. Hornblende  granite  is  quite  superior  to  the  first  two  classes  of 
granite  on  account  of  having  nearly  15  per  cent  of  that  tough  minera; 
present;  in  fact,  it  compares  favorably  with  any  of  the  coarse  grained 
rocks  for  the  same  reason.  The  fresh  diabase  and  basalts  are  superior 
to  the  rhyolites  and  andesites  on  account  of  the  higher  percent  of 
pyroxenes  and  amphiboles.  The  altered  basalts  and  diabases  are  inferior 
to  the  unaltered  ones  as  would  be  expected  on  account  of  the  weakening 
influence  of  the  softer  secondary  minerals. 

Porous  rocks  like  pumice  or  cellular  basalt  will  not  give  as  good 
results  from  the  standpoint  of  wear  as  obsidian  and  compact  or  dense 
basalt.  The  glassy  rocks  like  obsidian  or  those  partly  glass  and  partly 
micro-crystalline,  like  some  rhyolites  and  basalts,  will  be  tough  and 
behave  similarly  to  quartz  since  they  have  no  cleavage  but  break  in 
smooth  curves  like  glass. 

SEDIMENTARY  ROCKS. 

The  sedimentary  rocks  consist  of  materials  which  have  already  formed 
a part  of  pre-existing  rocks  and  have  been  deposited  either  by  water  or 
wind  after  being  moved  from  their  former  position.  When  carried  by 
my  transporting  agency,  such  as  wind  or  water,  rock  waste  becomes 
sediment  and  sooner  or  later  is  deposited  as  such.  Some  of  the  material 
picked  up  and  transported  by  running  water  is  left  at  the  bases  of  slopes 
end  hills  from  which  it  is  washed.  Some  is  left  on  flats  through  which 
streams  flow,  but  a large  part  of  it  is  carried  to  the  sea  and  distributed 
on  the  sea  floor.  The  coarser  parts  of  the  sediment  carried  to  the  sea 
is  left  near  the  shore  while  the  finer  parts  are  taken  farther  out.  This 
*s  seen  along  many  coasts  where  the  gravel  of  the  shore  line  grades 
out  into  sand  and  this  into  mud  as  distance  from  the  shore  increases. 
Thus  it  comes  about  that  coarser  materials  are  more  or  less  separate 
from  the  finer. 

After  the  sediments  such  as  gravel,  sand,  clays  and  muds  are  sorted 
and  deposited,  they  may  b^  cemented  into  more  or  less  solid  rock  by 
deposition  of  mineral  matter  held  in  solution  in  water.  This  cement 
binds  the  particles  together  into  rock  much  the  same  as  lime 
binds  sand  together  in  mortar.  Cemented  gravel  is  called  conglomerate. 
Cemented  sand  is  sandstone,  while  cemented  muds  or  clays  is  called 
shale.  This  cementing  process  obtains  in  all  degrees  of  perfection.  If 
the  cementing  material  is  of  good  quality  and  if  the  voids  and  pore 
spaces  between  these  sedimentary  grains  are  well  filled  the  result  will 
be  a very  hard  and  compact  rock.  On  the  other  hand,  should  the 
cementing  material  be  of  inferior  grade  or  only  present  in  small  amounts 
between  the  grains,  it  is  evident  that  the  quality  of  the  rock  will  be 
much  inferior  to  that  in  the  first  case.  This  principle  might  be  illus- 
trated in  the  case  of  mixing  concrete,  by  comparing  the  two  conditions 
where  excellent  cement  is  used  and  in  sufficient  quantity  to  bind  the 
particles  well  together,  with  an  inferior  grade  of  cement  or  insufficient 


PLATE  4 — Showing  the  ravelling  effect  of  a macadam  road  due  to  dry  weather.  Binding  power  is  here  destroyed  because 
insufficient  water  is  present  to  produce  efficient  capillarity  near  the  surface. 


17 


quantity.  Nature  uses  about  four  different  cementing  materials  in  these 
sedimentary  rocks,  viz:  silica,  calcium  carbonate,  iron  oxide  and  fine 
clay  or  mud.  In  case  any  one  of  the  last  three  cementing  materials  are 
used,  no  matter  how  great  the  quantity  of  cementing  materials,  the 
resultant  rock  will  be  in  almost  every  case  of  a very  friable  and  crumbly 
nature,  owing  to  the  weakness  of  the  bond.  In  the  case  of  the  limestones 
tnis  weakness  is  due  to  the  cleavage  or  easy  breaking  directions,  and  in 
case  of  the  iron  oxide  and  clay  cementing  materials,  the  weakness  is 
due  to  the  soft  nature  of  the  cementing  materials.  In  case  of  the  silica 
the  bond  may  be  very  strong  indeed,  since  quartz  is  a very  hard,  tough 
and  resistant  material.  Sedimentary  rocks  if  thoroughly  cemented 
together  with  this  material  may  be  among  the  hardest  and  most  resistant 
rocks. 

Limestones  are  also  formed  almost  entirely  on  the  ocean  floor.  These 
rocks  are  formed  by  the  accumulation  of  organic  remains  and  organic 
secretion  of  a calcareous  nature  as  well  as  chemical  precipitation  of 
calcium  carbonate.  Limestones  are  almost  entirely  made  up  of  the 
minerals  calcite  and  dolomite  which,  when  coarsely  crystalline  are 
usually  brittle  and  friable. 

On  examination  of  the  sedimentary  rocks  for  road  materials  we  find 
them  in  general  quite  inferior  to  the  igneous  class.  The  sandstones  as 
a rule  give  a very  high  percentage  of  wear  on  account  of  their  crumbly 
uature  due  to  insufficient  cementing  material  or  an  inferior  quality. 
There  are  some  exceptions,  however,  for  we  find  some  sandstones  so 
Lard,  firm  and  compact  that  they  break  under  the  hammer  very  much 
like  igneous  rocks  and  may  even  take  a good  polish.  Such  rocks  from 
the  standpoint  of  durability  would  make  good  road  materials.  Conglom- 
erates would  be  no  better  than  gravel  and  much  harder  to  obtain  and 
prepare  for  the  road.  Limestones,  if  coarsely  crystalline  will  give  a 
high  percentage  of  wear  owing  to  the  soft  nature  and  cleavage  of  the 
calcite  of  which  it  is  principally  composed.  Here  again  we  have  some 
exceptions  and  some  of  the  very  fine  grained  compact  limestones  are 
fairly  tough  and  give  a low  percent  of  wear.  Probably  the  most 
important  factor  in  connection  with  a limestone  for  a road  material  is 
its  value  as  a binder  for  macadam  roads.  This,  however,  will  be  dis- 
cussed under  cementing  or  binding  value  of  rocks  in  macadam  roads 
and  need  not  be  taken  up  here.  Shales  are  usually  too  soft  to  be  con- 
sidered for  road  materials. 

METAMORPHIC  ROCKS. 

The  metamorphic  rocks  are  those  which  originally  were  sedimentary 
or  igneous  and  have  been  changed  either  in  mineral  composition,  or  in 
structure,  or  both,  so  they  present  different  appearances  and  character- 
istics from  the  rocks  from  which  they  were  formed.  The  principal 
characteristics  of  most  metamorphic  rocks  are  their  foliated  structure 
due  to  the  more  or  less  parallel  arrangement  of  their  mineral  components, 
especially  the  mineral  mica.  The  foliated  metamorphic  rocks  in  general 

1-3 


18 


make  poor  road  materials  because  these  planes  of  foliation  are  planes 
of  weakness,  or  natural  cleavage  in  the  rock.  This  natural  cleavage  is 
due  almost  entirely  to  the  fact  that  the  mica  grains  or  crystals  are 
oriented  parallel  to  the  plane  of  foliation,  and  since  the  mineral  mica 
has  an  easy  cleavage  in  this  plane  these  foliated  rocks  give  way  easily 
along  the  mica  flakes  and  thus  we  find  that  these  foliated  rocks  are 
usually  very  friable  and  give  a high  percentage  of  wear. 

WEATHERING  OF  ROCKS  AND  HOW  IT  AFFECTS  THEM  FOR 
ROAD  MATERIALS. 

Weathering  is  the  term  applied  to  all  those  natural  processes  which 
tend  to  loosen  or  change  the  rocks  at  or  near  the  surface  of  the  earth. 
The  rain  which  falls  upon  the  surface  of  exposed  rock  and  that  which 
sinks  down  through  the  soil  to  the  solid  rock  below,  dissolves  slowly 
some  of  the  constituents  of  the  rock.  This  tends  to  make  the  rock 
porous  at  first  and  later  to  crumble  in  some  cases,  while  in  others  this 
dissolving  action  by  the  water  produces  new  minerals  out  of  the  old 
ones  and  these  we  call  secondary  minerals.  We  have  already  found 
that  secondary  minerals  are  almost  always  soft  and  friable,  and  conse- 
quently any  rock  which  contains  any  considerable  quantity  of  these 
minerals  would  be  softer  than  it  was  originally.  In  general  then,  we 
find  that  rocks  which  are  weathered  are  inferior  in  hardness  and  tough- 
ness and  give  a higher  percentage  of  wear  than  in  their  unaltered  or 
fresh  condition. 

Some  rocks,  especially  the  igneous  ones,  by  weathering  change  their 
physical  properties  to  such  an  extent  that  they  no  longer  resemble  the 
fresh  unaltered  rock  at  all.  Basic  igneous  rocks  like  basalt  and  gabbro 
when  weathered  change  from  the  dark  brown  or  black  color  to  a lighter 
brown  or  red  color  owing  to  the  change  of  the  iron  silicates  to  iron 
o>:ide  whose  natural  color  is  light  brown  or  red.  A large  number  of  the 
red  hills  in  the  Willamette  Valley  have  their  soils  painted  red  by  the 
iron  oxide  which  was  derived  from  the  weathering  of  the  basalts  and 
diabases  which  may  be  found  practically  unaltered  only  a few  feet  below 
the  surface. 

All  igneous  rock  masses  are  fissured  or  broken  up  into  angular  blocks, 
varying  in  size  from  a number  of  feet  in  length,  breath  and  thickness  to 
small  sizes  only  a few  inches  in  each  dimension.  These  cracks  or 
fissures  make  easy  roads  for  the  water  to  begin  its  work  of  rock 
weathering  and  as  the  work  of  decay  proceeds  each  block,  whether  large 
or  small,  becomes  separated  from  its  neighbor  by  a space  of  varying 
thickness  of  softer  weathered  material  between.  Before  these  blocks 
have  entirely  disappeared  we  find  them  on  the  surface  as  rounded 
masses  or  “niggerheads”.  They  are  called  by  the  geologist  “boulders 
of  weathering”.  These  masses  are  often  entirely  unaltered  only  a few 
inches  from  the  surface.  Fig.  2 shows  a group  of  these.  Fig.  3 gives 
some  idea  of  the  weathered  effect  close  to  the  surface.  In  some  cases 
the  iron  oxide  on  the  surface  of  these  boulders  become  leached  out  by 


19 


the  action  of  the  rain,  and  as  a reouit  the  old  basalt  boulder  becomes 
almost  white  on  the  surface.  The  white  minerals  are  secondary  minerals 
such  as  kaolin,  serpentine  and  talc.  There  are  a number  of  localities 
in  the  Willamette  Valley  where  these  light  colored  boulders  outcrop. 
Should  a person  suggest  that  these  boulders  were  really  basalt  and  that 
the  fresh  material  could  be  opened  up  only  a few  feet  below  the  surface 
he  would  in  most  cases  be  ridiculed. 

Some  authorities  claim  that  rock  weathering  is  a factor  to  be  considered 
in  the  durability  of  macadam  roads.  The  claim  has  been  made  that 
such  minerals  as  the  feldspars  will  break  down  from  the  standpoint 
of  decay  and  thus  materially  affect  the  rocks’  durability.  This  is  not 
in  accordance  with  the  facts  and  the  writer  doubts  if  the  weathering 
factor,  from  a purely  chemical  standpoint,  is  of  sufficient  importance  to 
warrant  consideration  in  a road  material  discussion.  The  weathering 
or  decay  of  the  ordinary  rock  making  minerals  is  so  extremely  slow  as 
to  be  scarcely  noticeable  in  the  period  of  years  involved  in  the  life  of  an 
ordinary  macadam  road.  It  is  true  that  such  minerals  as  feldspars, 
calcite  and  dolomite  grind  up  easily  under  traffic  but  the  reason  as  has 
already  been  given  is  on  account  of  their  friable  or  crumbly  nature  due 
largely  to  their  cleavage.  It  must  not  be  understood  in  this  connection 
that  a weathered  rotten  rock  would  be  an  economical  road  material. 
The  discussion  has  entirely  to  do  with  the  decay  of  fresh  material  after 
it  has  been  placed  upon  the  road.  Before  dismissing  this  discussion, 
however,  it  should  be  stated  that  for  macadam  work  a small  amount  of 
v eathered  material  if  used  cautiously  is  not  a detriment,  but  a positive 
advantage,  owing  to  the  increased  amount  of  screenings  produced  and 
therefore  aiding  in  the  binding  effect.  We  have  already  found  that  these 
secondary  minerals  formed  by  weathering  are  of  a crumbly  or  friable 
nature.  During  the  process  of  crushing  these  soft  minerals  crumble 
more  readily  than  the  fresh  ones  and  thus  produce  a larger  amount  of 
fines  or  screenings.  These  are  found  to  be  excellent  as  a binder  in 
macadam  roads.  Limestone  has  long  been  considered  as  an  excellent 
material  for  a binder  for  harder  rocks  which  lack  binding  qualities.  Its 
peculiar  qualifications  in  this  regard  can  be  best  explained  for  the  same 
reason,  namely,  that  it  produces  a larger  amount  of  extra  fine  screenings 
for  binder.  This  is  a vital  point  in  the  economics  of  road  construction 
because  few  rocks  produce  sufficient  screenings  in  proportion  to  the 
coarser  grades,  to  bind  them  properly. 

DESCRIPTION  OF  LABORATORY  TESTS. 

The  most  important  properties  of  rocks  by  virtue  of  which  they  are 
adapted  for  road  materials  as  discussed  in  most  modern  treatises  on 
the  subject  of  road  construction  are  hardness,  toughness,  and  cementing 
or  binding  qualities  of  the  dust,  and  finer  particles  of  the  rock.  The 
laboratory  tests  for  approximating  these  properties  as  usually  made  in 
the  laboratory  are  as  follows: 

(Bulletin  No.  31,  Office  of  Public  Roads,  page  23.) 


Pirate  5. — Basalt  quarry  on  Skinner  Butte,  Lane  county.  Columnar  jointing  due  to 
contraction  in  process  of  cooling. 


21 


“Percentage  of  wear  represents  the  amount  of  material  under  0.16  cm, 
in  diameter  lost  by  abrasion  from  a weighed  quanity  of  rock  fragments 
of  definite  size.  It  is  determined  in  the  following  manner:  The  rock 
sample  is  broken  into  pieces  that  will  pass  through  a 2.4  in.  ring  but 
not  through  a 1.2  in.  ring,  and  after  being  thoroughly  cleansed,  dried 
and  cooled,  5 kgs.  are  weighed  and  placed  in  a cast  iron  cylinder  (34  cm. 
deep  by  20  cm.  in  diameter)  closed  at  one  end  and  having  a tight-fitting 
iron  cover  at  the  other.  This  cylinder  is  one  of  four  attached  to  a 
shaft  so  that  the  axis  of  each  is  inclined  at  an  angle  of  30  degrees  with 
that  of  the  shaft.  These  cylinders  are  revolved  for  five  hours  at  the 
rate  of  2,000  revolutions  per  hour  during  which  the  stone  fragments 
are  thrown  from  one  end  of  the  cylinder  to  the  other  twice  in  each 
revolution.  At  the  end  of  the  five  hours  the  machine  is  stopped,  the 
cylinder  opened  and  their  contents  poured  into  a basin,  in  which  every 
stone  is  carefully  washed  to  remove  any  adherent  detritus.  This  abraded 
material  is  then  thoroughly  dried,  and  from  the  amount  lost  below  0.16 
cm,  the  percent  of  wear  is  estimated. 

Hardness  is  the  resistance  which  a material  offers  to  the  displacement 
of  its  particles  by  friction,  and  varies  inversely  as  the  loss  in  weight  by 
grinding  with  a standard  abrasive  agent.  The  test  is  made  in  the  follow- 
ing manner:  The  test  piece  in  the  form  of  a cylinder  about  three  inches 
in  length  by  one  inch  in  diameter  is  prepared  by  an  annular  core  drill  and 
placed  in  the  grinding  machine  in  such  a manner  that  the  base  of  the 
cylinder  rests  on  the  upper  surface  of  a circular  grinding  disk  of  cast 
iron,  which  is  rotated  in  a horizontal  plane  by  a crank  movement.  The 
specimen  is  weighed  so  as  to  exert  a pressure  of  250  grams  per  square 
centimeter  against  the  disk,  which  is  fed  from  a funnel  with  sand  of 
about  1 Vz  mm,  in  diameter.  After  1,000  revolutions  the  loss  in  weight  of 
the  sample,  is  determined  and  the  coefficient  of  wear  obtained  by 
deducting  one-third  of  this  loss  from  20. 

Toughness  as  here  understood  is  the  power  possessed  by  a material 
to  resist  fracture  by  impact.  The  test  piece  is  a cylindrical  rock  core 
similar  to  that  used  in  determining  hardness,  and  the  test  is  made  with 
an  impact  machine  constructed  on  the  principle  of  a pile  driver.  The 
blow  is  delivered  by  a hammer  weighing  two  kg.  which  is  raised  by  a 
sprocket  chain  and  released  automatically  by  a concentric  electromagnet. 
The  test  consists  of  a 1 cm,  fall  of  the  hammer  for  the  first  blow  and 
an  increased  fall  of  1 cm.  for  each  succeeding  blow  until  failure  of  the 
test  piece  occurs.  The  number  of  blows  required  to  cause  this  failure 
represents  the  toughness. 

The  cementing  value  or  binding  power  of  a road  material  is  the 
property  possessed  by  a rock  dust  to  act  as  a cement  on  the  coarser 
fragments  comprising  crushed  stone  or  gravel  roads.  This  property  is 
a very  important  one  and  is  determined  approximately  as  follows: 

One  kg.  of  the  rock  to  be  tested  is  broken  sufficiently  small  to  pass 
through  a 6 mm.  but  not  a 1 mm.  screen.  It  is  then  moistened  with  a 
sufficient  amount  of  water  and  placed  in  an  iron  ball  mill  containing 


22 


two  chilled  iron  halls  weighing  25  pounds  each  and  revolved  at  the  rate 
of  2,000  revolutions  per  hour  for  two  hours  and  a half  or  until  all  the 
material  has  been  reduced  to  a thick  dough,  the  particles  of  which  are 
not  above  0.25  mm.  in  diameter.  About  25  grams  of  this  dough  is  then 
placed  in  a cylindrical  metal  die,  25  mm.  in  diameter,  and  by  means  of  a 
specially  designed  hydraulic  press,  known  as  a briquette  machine  is 
subjected  to  a momentary  pressure  of  100  kg.  per  square  centimeter. 
Five  of  the  resultant  briquettes,  measuring  exactly  25  mm.  in  height  are 
taken  out  and  allowed  to  dry  for  12  hours  in  air  and  12  hours  in  a 
hot  oven  at  100  degrees  C.  After  cooling  in  a desiccator  they  are  tested 
by  impact  in  a machine  especially  constructed  for  the  purpose.  This 
machine  is  somewhat  similar  to  that  used  in  determining  the  toughness 
and  the  blow  is  about  the  same,  excepting  that  it  is  given  by  a 1 kg. 
hammer  and  the  distance  of  drop  does  not  exceed  10  cm.  The  standard 
fall  of  the  hammer  for  a test  is  1 cm.  and  the  average  number  of  blows 
required  to  destroy  the  bond  of  cementation  in  the  five  briquettes 
determines  the  cementing  value. 

The  specific  gravity  is  the  weight  of  the  material  compared  with  that 
of  an  equal  volume  of  water,  and  is  obtained  by  dividing  the  weight 
in  air  of  a rock  fragment  by  the  difference  of  its  weight  in  air  and  water. 
Given  the  specific  gravity,  the  weight  per  cubic  foot  of  a rock  is  found 
by  multiplying  this  value  by  62.5  pounds,  the  weight  of  a cubic  foot 
of  water. 

DISCUSSION  OF  THE  YALUE  OF  LABORATORY  TESTS. 

The  abrasion  test  for  giving  the  percentage  of  wear  as  described  above 
is  one  of  the  most  useful  of  laboratory  tests.  It  gives  the  practical  road 
builder  some  very  useful  information  in  that  it  measures  approximately 
the  property  of  a rock  to  withstand  the  grinding  action  of  severe  traffic. 
The  test  is  of  value  only  in  so  far  as  the  conditions  are  duplicated  but 
it  seems  probable  that  the  results  in  the  two  cases  would  be  fairly 
proportional. 

The  laboratory  test  for  hardness  is  of  no  great  importance,  since  it 
fails  to  give  any  information  which  is  not  given  by  the  test  for  abrasion. 
These  two  tests  agree  so  closely  that  the  labor  involved  in  making  this 
test  is  not  warranted  from  a practical  standpoint. 

Toughness  as  measured  in  the  laboratory  is  closely  related  to  the 
percent  of  wear,  as  the  results  in  most  cases  approximately  agree.  As 
would  be  expected  a tough  rock  will  give  a low  percentage  of  wear.  The 
main  difficulty  with  this  test  is  to  secure  a sample  for  a test  piece  which 
will  represent  the  average  condition  in  the  rock  being  tested.  This 
difficulty  arises  for  a number  of  reasons:  the  test  piece  often  contains 
an  incipent  fracture  which  causes  the  piece  to  give  way  under  the  ham- 
mer along  this  plane  of  weakness  and  as  a result  the  variation  is  great. 
Again  in  foliated  rocks  the  result  means  very  little  because  if  hammered 
at  right  angles  to  the  plane  of  foliation  the  result  would  obviously  be 
very  different  from  that  if  hammered  parallel  to  this  plane.  It  is  evident 


23 


from  this  that  the  general  results  from  the  impact  test  must  give  a wide 
range  of  variation. 

The  test  for  absorption  of  water  is  not  so  important  in  the  Willamette 
Valley  as  it  would  be  in  regions  of  colder  climate.  The  destructive  effect 
of  frost  as  measured  by  this  test  would  be  almost  negligible  in  this 
climate. 

The  specific  gravity  of  the  great  majority  of  rocks  used  for  roai 
material  is  fairly  constant,  occuring  usually  between  the  limits  of  2.65 
to  3.60.  As  a qualification  for  road  materials  the  heavier  rocks  such  as 
basic  igneous  ones,  will  be  somewhat  superior  to  the  lighter  weight  rocks 
The  specific  gravity  would  also  be  useful  in  determining  the  weight  of 
a large  amount  of  rocks  and  would  be  convenient  in  computing  freight 
rates. 

CEMENTING  OR  BINDING  VALUE  OF  ROCKS  IN  MACADAM  ROADS. 

Most  authorities  on  road  construction  claim  that  rock  powder  or  dust 
when  wet  has  a tendency  to  set  or  recrystallize,  and  by  virtue  of  this 
setting  quality  it  binds  its  particles  together  much  the  same  as  lime 
hardening  in  mortar  produces  a bond  between  its  particles.  It  is  also 
claimed  that  some  rocks  are  so  absolutely  void  of  this  property  that  it  is 
impossible  to  compact  them  either  with  a road  roller  or  under  traffic. 
With  these  claims  we  are  forced  to  take  issue,  largely  because  they  are 
not  substantiated  by  the  results  obtained  in  practical  road  making.  In 
the  first  place,  it  has  been  proved  in  a large  number  of  cases  over  the 
country  that  such  rock  as  quartzites  and  cherts  which  have  a minimum 
cementing  value  according  to  the  usual  test,  make  some  of  the  best 
macadam  material.  A large  number  of  our  best  basalts  in  the  Willamette 
Valley  have  very  poor  cementing  values  if  considered  from  the  stand- 
point of  the  laboratory  test,  and  yet  there  is  no  difficulty  in  binding  these 
materials  in  macadam  roads.  In  fact,  in  a number  of  cases  these  basalts 
have  been  used  in  the  valley  for  a number  of  years  and  have  given 
excellent  results.  It  is  found  that  a little  “dirty  sand”  or  gravel  screen- 
ings is  all  that  is  necessary  for  a binding  material  where  there  is  a lack 
of  rock  screenings  to  fill  the  voids. 

This  effect  of  binding  the  rock  fragments  and  particles  together  in  i\ 
macadam  road  can  best  be  considered  from  two  separate  and  distinct 
causes;  first,  the  mutual  interwedging  effect  of  contiguous  rock  particles 
when  compacted  as  much  as  possible,  and,  second,  the  binding  effect 
caused  tv  the  ca  illary  action  of  water.  This  wedging  effect  is  best  illus- 
trated by  noting  the  fact  that  in  the  process  of  construction  of  any 
macadam  read  the  surface  after  No.  1 and  No.  2 have  been  laid  and 
rolled,  before  the  screenings  have  been  put  on,  will  sustain  a load  if  care- 
fully applied,  nearly  equal  to  that  of  the  finished  macadam.  This  result 
is  obtained  almost  entirely  on  account  of  this  wedging  effect  and  because 
of  this  a heavy  load  applied  on  a small  area  on  such  a surface  in  being 
transmitted  down  through  six  inches  of  crushed  tightly  wedged  rock, 
will  be  distributed  over  an  area  on  the  surface  of  the  subgrade  many 


PivATE  6. — U.  S.  object  lesson  road  near  Fair  Grounds,  Marion  County.  Note  the  fact  that  there  is  no  main 
traveled  track  on  any  part  of  the  surfaced  road,  due  largely  to  the  low  crown. 


25 


times  as  large.  Thus  we  see  that  a macadam  road  is  able  to  support  its 
load  almost  entirely  by  virtue  of  its  interwedging  effect  between  its  an- 
gular rock  fragments.  However,  this  does  not  sufficiently  hold  each 
rock  fragment  in  its  wedged  position,  because  the  surface  particles  can 
easily  be  displaced.  This  is  the  peculiar  office  of  the  finer  rock  dust  and 
water,  as  will  be  seen  below. 

The  cementing  test  as  is  usually  carried  out  gives  very  little  practical 
information  for  the  use  of  the  road  builder,  because  there  seems  to  be 
very  little  in  common  between  the  conditions  which  obtain  in  the  macadam 
road  with  that  in  the  laboratory.  In  the  completed  macadam  road  the 
tiny  capillary  pore  spaces  are  nearly  or  quite  filled  with  water  while 
in  the  labarotary  the  water  in  these  capillary  spaces  is  supposed  to  be 
all  baked  out.  It  seems  to  the  writer  that  this  is  a very  vital  point  and 
one  that  makes  the  laboratory  test  for  cementing  value  worthless. 

It  would  be  reasonable  to  conclude  that  oridinary  clay  has  as  high  a 
cementing  value  as  the  best  rock  dust,  if  this  test  is  accepted  as  con- 
clusive. It  is  only  necessary  to  mix  the  clay  with  water  until  it  is 
made  into  a thick  dough.  “About  25  grams  of  this  dough  is  then  placed 
in  a cylindrical  metal  die  and  by  means  of  a specially  designed  hydraulic 
press  known  as  a briquette  machine  is  subjected  to  momentary  pressure 
of  100  kilograms  per  square  centimeter.  Five  of  the  resultant  briquettes 
measuring  exactly  25  millimeters  in  height  are  taken  out  and  allowed  to 
dry  twelve  hours  in  air  and  twelve  hours  at  100  degrees  C.  After  cooling 
in  a desiccator  they  are  tested  by  impact  in  a machine  especially  con- 
structed for  the  purpose.  The  standard  fall  of  the  hammer  is  one 
centimeter  and  the  average  number  of  blows  required  to  destroy  the 
bond  of  cementation  in  the  five  briquettes  determines  the  cementing 
value.”  Under  this  treatment  the  clay  gives  a higher  test  for  cementing 
value  than  the  best  rock  dust,  while  the  facts  are,  clay  has  no  cementing 
value  because  when  wetted  it  immediately  becomes  soft  and  plastic. 

Without  question  it  is  the  action  of  surface  tension  of  water  in  these 
capillary  spaces  between  the  tiny  particles  that  is  a most  important  and 
vital  factor  in  the  binding  material  of  a macadam  road.  In  order  to 
prove  the  importance  of  water  in  the  binding  material  of  a road  it  is 
only  necessary  to  note  the  fact  that  our  dry  Oregon  summers  are  the 
worst  enemy  to  macadam  roads  that  we  have.  See  Fig.  4.  A great 
number  of  our  macadam  roads  begin  to  ravel  during  the  long  dry  sum- 
mer but  immediately  become  firm  and  hard  when  the  rains  resume  in 
the  fall.  Again  any  practical  road  builder  in  the  country  will  attest  to 
the  fact  that  the  easiest  macadam  roads  to  keep  in  repair  are  those 
which  are  situated  in  heavy  timber,  thus  shutting  out  the  sun.  Under 
these  conditions  the  tiny  capillary  tubes  reach  the  very  surface  of  the 
road  and  thus  hold  or  knit  each  tiniest  particle  to  its  neighbor. 

If  it  were  possible  to  make  a microscopic  examination  of  a section  of 
a well  made  macadam  road  it  would  be  found  that  the  voids  between 
the  largest  pieces  of  rock  would'  be  filled  with  smaller  pieces  of  rock, 
and  the  voids  between  these  smaller  pieces  would  again  be  filled  by  much 

1^4 


26 


smaller  pieces  and  so  on  until  the  finest  particles  filling  the  very  tinest 
voids  would  be  microscopic  in  size.  Under  this  arrangement  the  condi- 
tions for  capillarity  would  be  as  complete  as  in  the  finest  clay.  Our 
microscope  would  show  that  each  particle  of  rock  or  dust  was  completely 
surrounded  by  a tiny  film  of  water,  or  in  other  words  that  the  whole 
mass  was  completely  ramified  by  an  intricate  network  of  tiny  capillary 
tubes,  which  tend  to  bind  the  mass  together  like  so  many  threads.  The 
strength  of  this  water  bond  lies  in  the  fact  that  these  tubes  are  so  tiny 
that  water  passes  through  them  very  slowly  even  if  under  great  pressure 
and  if  any  physical  force  would  tend  to  move  any  single  particle  in  any 
direction  it  is  evident  that  it  could  not  move  without  moving  the  water 
in  the  capillary  tubes  in  that  neighborhood.  Now  since  it  requires  a 
great  force  to  move  water  rapidly  in  these  tiny  capillary  tubes  the 
resistance  to  the  movement  of  the  aforesaid  particle  would  be  very  great. 
This  principle  is  the  keynote  in  the  theory  of  the  binding  action  in  a 
macadam  road.  This  is  the  obvious  reason  why  the  practical  road 
builder  finds  that  clean  sand  is  a very  poor  binding  material  while  bank 
sand  which  contained  a considerable  amount  of  dirt  or  silt  is  one  of  the 
best  materials  he  can  get.  This  is  caused  by  the  fact  that  the  dirty  sand 
has  a sufficient  amount  of  the  finer  particles  to  fill  the  voids  between  the 
coarser  sand  grains,  while  these  finer  particles  have  their  voids  again 
filled  by  smaller  particles  and  so  on  and  thus  the  conditions  for  more 
perfect  capillarity  are  fulfilled.  In  case  the  clean  sand  is  used  as  a 
binder  the  voids  between  these  coarse  grains  are  comparatively  large, 
the  capillarity  being  thus  very  greatly  diminished.  The  strength  of 
capillarity  measured  by  the  height  of  rise  in  a tube  above  its  hydrostatic 
level,  is  inversely  proportional  to  the  diameter  of  the  tube,  that  is  to 
say  reducing  the  diameter  of  the  tube  to  one-half  doubles  the  heighth 
that  water  may  be  raised  in  the  tube,  by  capillarity,  or  reducing  the 
diameter  to  1-100  enables  the  water  to  rise  100  times  as  high. 

In  order  that  the  above  discussion  may  not  prove  misleading  a few 
words  of  caution  will  not  be  out  of  place.  Some  might  infer  that  since 
a little  dirt  or  silt  is  very  beneficial  in  binding  material  for  a macadam 
road,  that  more  would  be  better  and  thus  lead  to  a promiscuous  use 
of  clay  as  a binder.  This  would  be  an  unfortunate  mistake  and  one 
that  is  often  made  by  the  road  builder.  By  referring  once  more  to 
our  microscopic  section  through  a macadam  road  it  is  evident  that  if 
we  have  present  a greater  amount  of  particles  of  a certain  size  class 
than  is  required  to  fill  the  voids  of  the  next  coarser  class  the  tendency 
will  be  to  destroy  the  wedging  effect  between  the  pieces  or  particles  of 
said  coarser  class.  It  is  evident  that  the  amount  of  fine  clay  particles 
which  would  be  required  to  fill  the  voids  between  the  next  coarser 
particles  would  be  a very  small  percent  of  the  total  volume  of  the 
macadam  material. 

It  is  of  the  utmost  importance  that  a field  examination  be  made  in 
connection  with  the  laboratory  test.  Unless  this  is  done  exhaustive 
laboratory  tests  will  often  be  made  upon  very  inferior  material  when 


27 


excellent  material  is  at  Land,  in  otner  words,  it  requires  as  much  skill 
to  take  the  sample  as  it  does  to  determine  the  fitness  of  the  material. 
Very  often  a sample  of  weathered  rock  of  inferior  quality  is  sent  in  to 
the  laboratory  while  excellent  road  material  in  the  fresh  rock  would 
have  been  found  only  a few  feet  beneath  the  surface.  An  example  by 
way  of  illustration  will  suffice.  The  writer  has  in  mind  a particular 
hill  in  the  Willamette  Valley  from  which  a sample  had  been  taken  some 
time  since  and  sent  to  the  Department  of  Public  Roads,  Washington, 
D.  C.  Their  report  was  unfavorable  and  in  the  case  of  the  sample  sent 
in  was  entirely  correct.  On  account  of  this  authoritative  test  the  whole 
hill  was  abandoned  by  the  road  builders.  The  fact  is,  however,  that 
there  is  a large  and  favorably  located  outcrop  of  excellent  road  material 
on  that  same  hill  not  more  than  100  feet  from  where  the  above  sample 
was  taken,  it  being  a different  formation  and  an  entirely  different  type 
of  rock. 

ROAD  MATERIAL  SITUATION  BY  COUNTIES. 

BENTON  COUNTY. 

Benton  County’s  rocks  include  a considerable  amount  of  hard  igneous 
material  as  well  as  some  of  the  softer  sandstones  and  shales  which 
are  not  well  adapted  for  road  purposes.  The  exposed  outcrops  are  found 
entirely  in  the  foothills  and  a few  buttes  scattered  over  the  floor  of  the 
valley.  The  igneous  rocks  are  fairly  well  distributed  through  different 
parts  of  the  county. 

In  the  extreme  southern  end  of  the  county  are  numerous  outcrops  of 
a good  hard  basalt.  The  hills  two  miles  southwest  of  Monroe  are  made 
up  of  this  material.  A few  outcrops  are  found  near  the  county  line  one 
and  one-half  miles  south  of  Monroe,  but  in  this  section,  are  covered 
with  considerable  depth  of  soil.  By  prospecting  good  quarry  sites  should 
easily  be  obtained.  A number  of  good  outcrops  are  also  available  two 
miles  west  and  one  south  of  Monroe  in  the  vicinity  of  the  old  Belknap 
place.  These  rocks  give  excellent  tests  for  road  material. 

The  hills  immediately  west  and  northwest  of  Monroe  are  sandstone 
which  crumbles  very  readily  under  abrasion  and  are  entirely  unfit  for 
road  material.  Spring  Hill  one  and  one-half  mile  north  and  one-half 
mile  west  of  Monroe  on  the  south  side  of  the  C.  & A.  railroad,  is  made 
up  of  a good  quality  of  basalt.  An  excellent  quarry  could  be  located 
on  the  north  side  of  the  hill  at  this  point.  It  is  a particularly  desirable 
location  for  a site  because  of  the  transportation  facilities.  In  the  neigh- 
borhood of  Bellfountain  are  a few  outcrops.  Near  the  summit  on  the 
southwest  slope  of  the  Butte  just  east  of  Bellfountain  a medium  size 
grained  diabase  is  found,  but  no  outcrops  were  found  at  the  base  of 
the  hill.  An  outcrop  of  basalt  which  gives  excellent  tests  for  road 
material  is  found  two  and  one-half  miles  northwest  of  Bellfountain  in 
the  canyon  of  Rees  creek  just  above  the  N.  R.  Stauturf  place.  This  is  an 
excellent  site  for  a quarry  because  situated  well  above  the  road,  and 
would  require  little  or  no  stripping.  About  one  mile  southwest  of 


Pirate;  7. — Kwald  quarry  near  Salem  showing  extreme  fissured  condition  of  basalt. 


29 


Bellfountain  are  also  some  basalt  outcrops  and  by  prospecting  a good 
site  for  a quarry  could  probably  be  found.  On  the  J.  H.  Edwards  place 
one  and  one-half  mile  northeast  of  Bellfountain  quite  an  extensive  out- 
crop of  a good  hard  diorite  is  found.  This  material  will  make  a good 
road  metal,  although  it  is  not  so  good  as  basalt.  The  southwest  slope 
of  the  hill  will  be  a convenient  site  to  accommodate  a considerable  area, 
since  no  other  available  outcrops  are  near.  The  hills  for  four  or  five 
miles  north  of  Bellfountain  are  sandstone  which  is  unfit  for  road 
materials,  and  probably  very  few  if  any  outcrops  of  a good  road  rock 
can  be  found  in  this  section. 

On  the  Park  place  six  miles  south  of  Philomath  a small  intrusion  of 
basalt  in  sandstone  is  found.  This  material  is  of  fair  quality  for  road 
material  but  the  quarry  is  not  in  a favorable  site  for  the  economic 
handling  of  the  rock.  It  is  probable  that  more  favorably  situated 
outcrops  could  be  found  in  this  vicinity.  The  quarry  one-fourth  of  a 
mile  south  of  the  Park  quarry  is  a semi-consolidated  sandstone  and 
would  be  entirely  unfit  for  road  material.  Erwin  Butte  ten  miles  south 
of  Corvallis  on  the  Monroe  road  is  almost  entirely  sandstone  on  the 
surface.  Doubtless  the  main  mass  of  the  hill  is  basalt,  and  although 
but  one  point  is  found  where  the  basalt  is  exposed  a little  prospecting 
would  probable  locate  a good  igneous  rock  quarry  on  this  hill.  On  the 
south  slope  of  the  butte  on  the  Jesse  Foster  place,  about  two  and  one- 
half  miles  southwest  from  Erwin  Butte  a hard  dense  basalt  outcrop  is 
found  which  is  excellent  for  road  materials.  On  the  north  side  of  the  hill 
southwest  of  Philomath  is  found  an  outcrop  of  fine  grained  syenite. 
This  rock  like  the  above  mentioned  diorite  does  not  give  as  good  results 
for  road  materials  as  the  more  basic  denser  basalts.  It  is  a good  rock 
however  and  will  wear  well  under  any  ordinary  traffic.  Some  of  the 
streets  of  Philomath  have  been  macadamized  with  this  rock  with  good 
results.  The  southwest  side  of  the  same  hill  seems  to  be  made  up  of 
sandstone  which  should  be  avoided  in  searching  for  road  rock.  One 
mile  farther  south  on  Hartless  Hill  at  the  J.  H.  Melville  place  there  is 
found  an  outcrop  of  very  much  altered  basalt.  This  is  soft  and  easy  to 
quarry  but  the  material  thus  far  obtained  will  not  make  an  economical 
road  material.  It  grinds  up  readily  under  traffic  and  makes  a smooth 
road  quickly,  but  will  not  wear  well  enough  to  warrant  the  expense  of 
putting  it  on  the  road.  Such  weathered  rotten  basalt  is  no  better  than 
soft  sandstone  for  road  material.  An  effort  should  be  made  under  these 
conditions  to  find  points  where  fresh  basalt  can  be  obtained  with 
minimum  amount  of  stripping.  (See  selection  of  Quarry  Sites.) 

West  and  north  of  Philomath  are  found  a large  number  of  outcrops  of 
excellent  hard  trap  rocks.  West  from  Philomath  in  the  vicinity  of  the 
railroad  leading  to  Noon  Bros,  sawmill  are  numerous  outcrops  of  a 
granular  rock  called  diabase  which  is  good  material. 

A quarry  of  fresh  hard  basalt  is  opened  up  about  one  and  one-half 
miles  south  from  Wren  just  south  of  the  summit  of  the  hill.  On  the 
C.  & E.  railroad  between  Philomath  and  Wren  are  several  outcrops  of 


30 


basalt  rock  exposed  in  the  railroad  cuts.  Some  of  these  exposures  show 
good,  hard,  dense  material  and  will  make  excellent  quarry  sites. 

On  the  wagon  road  leading  to  Blodgett  following  the  railroad  many 
good  basalt  exposures  are  found,  sufficient  both  in  quality  and  quantity 
to  supply  this  neighborhood  with  excellent  road  material.  One  and  one- 
half  miles  from  Wren  on  the  road  leading  northwest  toward  Kings 
Valley  is  found  a basalt  quarry.  Some  of  the  rock  in  this  quarry  is 
excellent  and  hard  while  part  is  quite  soft.  By  intelligent  selection 
the  material  in  this  quarry  can  be  used  to  good  advantage.  Three 
miles  west  of  Corvallis  on  the  road  to  Wren  are  outcrops  of  diabase  of 
medium  size  grain  which  is  good  rock  for  macadam  and  from  this  point 
to  Wren  are  several  good  exposures  of  basalt. 

Northwest  of  Corvallis  one  and  one-half  miles  are  found  a few 
quarries  exposing  the  igneous  rock,  syenite.  This  is  a good  rock  for 
road  material  and  although  somewhat  inferior  to  good  fresh  dense  basalt 
will  give  very  satisfactory  results  as  a road  material.  The  hills  north 
of  Corvallis  on  west  side  of  Southern  Pacific  railroad  are  very  largely 
basalt.  A number  of  outcrops  have  been  opened  up  as  quarries  but  in 
no  case  was  there  found  fresh  unaltered  rock.  In  these  quarries  such 
as  Hahn’s  one  and  one-half  miles  northwest  from  Corvallis  near  Vine- 
yard hill,  the  Bauer  quarry  near  Mountain  View  school  house  and  Walter 
Wiles  quarry  near  the  north  county  line,  the  rock  is  so  much  weathered 
and  rotten  as  to  be  entirely  unfit  as  a road  material.  In  a number  of 
communities  where  the  practice  is  to  haul  rock  on  the  road  without 
crushing  or  rolling  these  rotten  rocks  are  quite  popular.  These  rocks 
make  a passable  road  in  the  winter  because  they  grind  up  readily  and 
make  a firm  enough  surface  to  support  the  ordinary  load.  These  roads 
will  not  give  sufficient  wear  however,  to  warrant  the  expense  of  putting 
this  material  on  the  roads,  when  only  a little  additional  expense  in 
crushing  and  rolling  a hard  rock  would  produce  an  excellent  macadam 
road  that  will  last  for  years.  Some  prospecting  should  be  done  in  these 
sections  to  find  if  possible,  points  where  the  fresh  rock  could  be  opened 
up  with  minimum  amount  of  stripping  of  soil  or  overburden.  On  the 
George  Lindeman  place  for  example  it  is  probable  that  a good  hard 
rock  quarry  could  be  opened  up  with  little  difficulty. 

East  of  the  Southern  Pacific  Railroad  and  north  of  the  Willamette 
river  the  outcrops  are  sandstone  and  probably  no  good  road  material 
can  be  found  in  this  area.  For  considerable  areas  in  Benton  County 
especially  south  of  Corvallis,  the  Willamette  river  gravels  will  be  the 
most  available  and  economical  materials  that  can  be  had.  If  the 
coarser  gravels  are  selected  and  crushed,  they  will  give  excellent 
results. 

CLACKAMAS  COUNTY. 

Clackamas  County  is  well  supplied  with  excellent  material  for  road 
building  as  well  as  being  well  distributed  over  the  county.  The  outcrops 
in  this  county  are  almost  entirely  basalt  which  might  be  divided  into 
two  classes  owing  to  their  difference  in  appearance.  The  dark  brown  or 


31. 


black,  dense,  very  fine  grained  basalt,  and  the  gray  basalts  which  are 
somewhat  more  coarsely  crystalline,  although  being  still  very  fine 
grained  rock.  These  gray  basalts  are  somewhat  more  porous  than  the 
dark  and  although  they  are  all  good  rocks  for  macadam  purposes  the 
dark  colored  more  dense  basalts  will  give  the  best  wear  under  heavy 
traffic.  These  lighter  colored  basalts  have  a higher  percentage  of  feldspar 
and  a lower  percent  of  pyroxene  than  the  dark  colored  ones.  As  com- 
pared with  these  we  find  the  dark  colored  basalts  having  less  amount  of 
feldspars  in  proportion  to  the  pyroxene  as  well  as  having  considerable 
amount  of  rock  glass  present. 

These  gray  or  light  colored  basalts  are  very  similar  to  those  found 
in  Multnomah  County  on  Rocky  Butte,  Kelly  Butte  and  west  of  Council 
Crest.  We  find  them  outcropping  along  the  Clackamas  river  in  the  neigh- 
borhood of  Baker’s  bridge  some  seven  miles  east  from  Oregon  City. 
They  are  found  outcropping  on  both  sides  of  the  river  canyon  from 
Baker’s  bridge  some  three  or  four  miles  east.  We  find  them  exposed 
again  in  large  quantities  on  both  bluffs  of  Clear  Creek,  west  of  Logan. 
From  this  point  to  Viola  they  are  found  outcropping  more  or  less  all 
along  the  creek  bluffs.  It  has  already  been  mentioned  in  the  discussion 
of  rock  weathering  how  these  basalts  change  in  color  to  reddish  or 
brownish  boulders  upon  the  surface.  These  are  found  scattered  all 
over  the  hills  in  this  section  and  are  due  to  the  decay  of  the  rock 
found  just  below  the  soil.  There  are  numerous  hill  sides  on  the 
Aberneathy  road  showing  outcrops  of  these  rounded  boulders  and  in 
favorable  areas  the  rock  could  be  easily  found  in  place  in  these  sections 
with  comparatively  small  amount  of  stripping. 

Still  farther  south,  we  find  these  same  light  colored  basalts  in  the 
neighborhood  of  Beaver  Creek.  There  are  numerous  areas  in  this  section 
where  the  erosions  of  small  streams  have  laid  bare  the  rocks  beneath 
making  favorable  points  for  quarry  sites.  Considerable  work  is  being 
done  in  road  building  in  this  section  as  well  as  farther  south  along  the 
Molalla  road  one  half  mile  north  from  Mulino  at  a cut  in  the  hill  which 
slopes  to  the  south  is  an  excellent  site  for  a quarry.  The  high  bluffs  on 
the  west  side  of  the  road  are  all  composed  of  an  excellent  fine  grained 
hard  basalt  somewhat  darker  in  color  than  the  ones  in  the  neighborhood 
of  Beaver  Creek  just  mentioned. 

This  is  a good  quarry  site,  first  because  it  is  favorably  situated  near 
the  road  and  also  because  little  or  no  stripping  would  be  required. 

At  a point  about  four  miles  east  of  the  town  of  Molalla  on  the  east 
side  of  the  river  are  found  outcrops  of  a good  hard  basalt  and  from  this 
point  to  Mulino  along  the  stream  bluffs  occur  a number  of  outcrops  of 
the  same  materal.  It  is  found  again  still  farther  south  of  Molalla  in 
the  Wilhoit  country.  Considerable  area  in  this  section  contain  outcrops 
of  good  dense  basalt  and  if  favorable  localities  are  selected  good  quarry 
sites  can  be  obtained  with  small  amount  of  stripping.  In  the  neighbor- 
hood of  Glad  Tidings  on  Rock  Creek  are  found  a few  outcrops  of  impure 
limestone.  This  rock  cannot  be  recommended  as  an  excellent  road 


Plate  8. — Kwald  quarry,  Marion  county. 


33 


material  if  used  by  itself  it  being  somewhat  soft  and  friable  and  easily 
grounded  up  under  traffic.  Such  rock  if  used  alone  makes  macadam 
roads  very  quickly  and  gives  excellent  results  at  first  but  are  not  adapted 
for  heavy  traffic.  Along  the  banks  of  the  Molalla  river  close  to  the 
water’s  edge  will  be  found  outcrops  of  sandstone  and  shales.  These 
rocks  are  not  at  all  adapted  for  road  making  purposes  being  easily 
ground  up  under  traffic  and  should  be  shunned  by  the  road  builder 
in  searching  for  material. 

Along  the  bluffs  of  the  Willamette  river  on  either  side  from  New  Era 
to  Oregon  City  are  found  high  bluffs  of  basalt,  50  to  100  feet  high 
standing  almost  vertically.  This  large  mass  of  rock  is  almost  entirely 
of  a dark  fine  grained  dense  variety  of  basalt  before  mentioned.  A 
number  of  excellent  quarry  sites  could  be  selected  in  this  locality  on 
account  of  the  convenience  of  transportation  being  accessable  either  to 
railway  or  water  transportation  on  the  river.  Farther  north  we  find 
these  same  dark  basalts  outcropping  on  the  Clackamas  river  near  Park 
Place,  as  well  as  in  the  hills  east  from  Clackamas  station.  Numerous 
basalt  outcrops  are  also  found  farther  down  the  Willamette  river  toward 
Portland.  In  the  neighborhood  of  Oswego  these  outcrops  are  especially 
prevalent.  In  this  section  care  needs  to  be  exercised  in  selecting  the 
more  dense  portion,  the  mass  here  being  made  up  of  layers  of  cellular 
basalt  interspersed  with  the  more  dense  varities  of  basalt.  This  has 
already  been  explained  as  coming  from  the  fact  that  gases  escaping  dur- 
ing the  cooling  makes  the  lava  sometimes  very  porous  or  sort  of  lava 
froth.  This  porous  lava  from  the  standpoint  of  macadam  materials 
should  be  shunned  as  far  as  possible  because  it  lacks  considerably  in 
wearing  qualities  as  compared  with  the  more  dense  varieties. 

These  outcrops  of  basalt  are  found  in  abundance  for  two  miles  to  the 
southwest  towards  Stafford.  In  the  neighborhood  of  Stafford  are  no 
very  important  outcrops  for  the  reason  that  they  are  largely  covered  too 
deep  with  soil. 

LANE  COUNTY. 

Lane  County  is  well  supplied  with  the  hard  dense  basic  igneous  rocks. 
With  the  exception  of  a few  stray  buttes  situated  here  and  there  on  the 
floor  of  the  main  valley,  these  rocks  are  confined  entirely  to  the  foot- 
hills bordering  the  valley  proper.  These  basic  rocks  are  all  dense  hard 
basalt  or  fine  grained  diabase  and  without  exception  give  excellent  tests 
as  road  metal.  The  hills  south  from  Eugene  from  the  Bailey  school  east 
to  Judkins  Point  are  all  basalt  and  have  numerous  points  which  would 
make  favorable  quarry  sites.  At  Judkins  Point  just  above  the  Southern 
Pacific  Railway  is  exposed  an  outcrop  of  excellent  hard  olivene  basalt 
while  just  below  near  the  road  is  a soft  sedimentary  rock  which  is  not 
fit  for  road  material.  The  Butte  just  south  of  Springfield  is  basalt  and 
considerable  of  this  material  has  been  used  on  the  roads  in  the  vicinity 
with  good  results.  Skinner’s  Butte  is  a porphyritic  basalt  being  made  up 
largely  of  feldspar  and  pyroxene.  This  is  one  of  the  most  perfect  ex- 
amples of  columnar  jointing  to  be  found  anywhere  in  the  valley.  See 


84 


Fig.  5.  This  is  an  excellent  road  material.  The  Rossman  Quarry  two 
°nd  one-half  miles  northwest  from  Eugene  is  a fine  grained  diabase,  has 
excellent  qualities  as  a road  material.  This  quarry  furnished  the 
material  for  building  the  Santa  Clara  road.  An  outcrop  of  basalt  of 
small  area  is  found  on  a low  hill  one  mile  west  from  Eugene  just  east 
of  the  road. 

In  the  vicinity  of  Oak  Hill  school  the  hills  for  two  miles  both  east 
and  west  are  sandstones  of  poor  quality  for  road  materials.  Rattle 
Snake  butte  farther  to  the  northwest  is  again  basalt  of  excellent  quality. 
A few  good  outcrops  are  found  still  farther  north  along  the  foothills 
Dut  no  detailed  examination  was  made  except  in  the  very  northern  part 
of  the  county.  About  two  miles  northeast  from  Springfield  where  the 
railroad  first  touches  the  hills  are  found  an  abundance  of  basalt  out- 
crops. Here  are  some  excellent  sites  for  quarries  both  from  the  stand- 
point of  their  proximity  to  railroad  transportation  as  well  as  requiring 
little  or  no  stripping.  Numerous  outcrops  of  the  same  material  are 
found  all  along  the  railway  from  this  point  to  Wendling.  The  hills  just 
east  of  the  McKenzie  river  from  Coburg  to  the  southeast  for  several 
miles  have  numerous  outcrops  of  the  same  hard  basalt.  At  a point  in 
the  hills  near  the  McKenzie  river  bridge  two  miles  southeast  from 
Coburg  is  an  excellent  quarry  site,  largely  on  account  of  its  situation 
on  railroad  and  wagon  road,  making  a good  distribution  point  for  either 
quarry  rock  or  gravels.  North  from  Coburg  the  first  foothills  contain  a 
number  of  basalt  outcrops,  the  most  available  being  a butte  one  and 
one-half  miles  north  from  Coburg,  Rockhill  three  mills  north  and  West 
Point  Hill  on  the  Lane-Linn  county  line. 

In  the  southern  part  of  Lane  county  in  the  vicinity  of  Cottage  Grove 
the  trap  rocks  are  well  distributed.  The  hills  immediately  on  the 
northwest  side  of  the  town  of  Cottage  Grove  extending  southwest  past 
the  cemetery  to  the  town  of  Latham  contain  only  outcrops  of  a 
volcanic  conglomerate  or  tuff.  This  rock  is  not  sufficiently  consolidated 
to  make  a good  road  material.  Beyond  Latham,  however,  on  the  west 
side  of  the  valley  the  hills  are  basalt,  there  being  numerous  excellent 
outcrops  from  this  point  to  beyond  the  Divide.  On  the  east  side  of 
the  valley  for  a distance  of  six  miles  south  from  the  town  of  Cottage 
Grove  the  hills  are  all  basalt.  A few  good  outcrops  are  found  on  the 
terrace  just  southeast  of  the  town.  The  quarry  from  which  the  material 
was  obtained  for  paving  the  city  streets  in  Cottage  Grove  is  about  one 
and  one-half  miles  north  from  the  city.  The  mass  is  excellent  columnar 
basalt  and  gives  good  results.  From  this  point  north  to  Cresswell  the 
valley  is  comparatively  narrow  and  the  hills  almost  entirely  trap  rocks. 
Lane  County  is  fortunate  as  well  as  some  of  the  neighboring  counties  in 
having  a large  amount  of  excellent  gravels  in  the  river  beds  which  when 
crushed  make  excellent  road  materials.  These  gravels  are  well  dis- 
tributed through  the  central  part  of  the  valley  and  will  accommodate 
a large  area  which  is  situated  at  prohibitive  distances  from  available 
deposits  in  the  foothills  on  either  side  of  the  valley. 


35 

LINN  COUNTY. 


Linn  County  is  also  very  fortunate  in  having  a goodly  supply  of  trap 
rocks  which  are  well  distributed.  A glance  at  the  map  will  show  a more 
or  less  continuous  line  of  outcrops  extending  from  the  vicinity  of  Kings- 
ton on  the  north  Santiam  river  through  the  county  in  the  vicinity  of 
Lebanon  and  Brownsville  to  the  Lane  county  line.  This  line  marks  rough- 
ly the  first  foothills  on  the  east  of  the  main  floor  of  the  Willamette  Val- 
ley. This  leaves  an  area  west  from  this  line  to  the  Willamette  river  of  ap- 
proximately four  hundred  square  miles  in  which  no  outcrops  or  rocks 
are  found  except  a few  stray  buttes.  It  is  evident  then  since  this  area 
averages  about  ten  miles  in  width  by  utilizing  the  gravels  in  the 
Willamette  river  the  maximum  haul  need  not  be  more  than  about  five 
to  seven  miles.  This  is  a far  better  distribution  of  road  materials  than 
is  usually  found  in  areas  of  equal  size. 

Along  the  Santiam  river  from  Kingston  to  Lyons  is  an  almost  un- 
limited mass  of  dense  black  basalt.  The  Santiam  river  has  cut  its  way 
through  this  mass  exposing  a bluff  on  the  south  side  of  the  river 
rising  from  50  to  150  feet  high.  Although  this  material  is  considerably 
weathered  on  the  surface  in  places  the  mass  as  a whole  is  excellent 
material  and  is  one  of  the  best  quarry  sites  in  the  Willamette  Valley 
for  getting  out  a large  quantity  of  rock.  Situated  upon  the  C.  & E. 
Railroad  makes  it  a good  distribution  point.  This  basalt  formation  is 
immediately  underlaid  by  sandstones  and  shales  which  are  very  inferior 
material  for  road  metal.  This  same  basalt  outcrops  over  a wide  area 
to  the  south  of  the  Santiam  in  the  vicinity  of  Kipsharts  Bluff  as  far  as 
the  town  of  Jordan.  Good  quarries  could  be  opened  up  almost  anywhere 
in  this  area. 

The  Mespelt  quarry  situated  about  two  and  one-half  miles  southeast 
froxr  Thomas  shows  a good  face  of  basalt  typical  of  a number  of  out- 
crops found  in  this  neighborhood.  It  is  very  hard,  black,  dense  and 
unaltered  and  as  good  rock  for  road  material  as  can  be  found  anywhere. 
Peterson’s  Butte  three  miles  southwest  from  Thomas,  has  some  good 
outcrops  of  basalt  which  will  make  good  road  material  and  some 
excellent  quarry  sites  could  easily  be  located.  The  southwest  slope  of 
this  butte  will  be  found  the  most  favorable  because  the  soil  is  thinner 
and  requires  less  stripping  as  has  been  noted  before  in  the  description 
of  the  general  geology  of  the  valley. 

On  the  west  slopes  of  Kees  Butte  one-half  mile  east  of  the  town  of 
Lebanon  is  an  excellent  quarry  of  fresh,  hard  black  basalt  exhibiting 
a very  fine  columnar  structure.  This  material  is  very  similar  to  the 
rock  in  the  Mespelt  quarry,  giving  excellent  tests  as  a road  material. 
This  is  a very  favorable  site  for  a quarry  being  near  the  railroad  and 
about  100  feet  above  the  wagon  road.  An  almost  unlimited  amount  of 
material  could  be  obtained  and  easily  handled.  About  two  and  one-half 
miles  northeast  of  Kees  Butte  some  excellent  outcrops  of  basalt  are 
found.  Between  this  point  and  Kees  Butte,  however,  is  a considerable 


Pirate  9. — Basalt  cliffs  along  the  Columbia  River,  Multnomah  County 


37 


area  covered  with  sandstone.  This  rock  in  common  with  nearly  all 
of  our  Pacific  Coast  sandstones,  is  not  sufficiently  consolidated  to  make 
good  material  for  road  construction.  If  used  upon  the  road  it  would 
soon  grind  to  powder. 

Ward’s  Butte  situated  about  one  and  one-half  miles  southwest  of 
Plainview  and  Saddle  Butte  three  miles  east  of  Shedd  are  solid  masses 
of  basalt.  This  rock  is  almost  identical  with  that  of  Kees  Butte.  A 
number  of  good  quarry  sites  could  be  located  upon  each  of  these  Buttes, 
the  southwest  slope  again  being  more  favorable.  The  rock  in  Saddle 
Butte  three  miles  east  from  Shedd  is  finely  fissured,  similar  to  the 
Ewald  quarry  in  Marion  county,  south  of  Salem,  and  on  this  account 
would  be  easily  handled  in  quarring  and  crushing.  The  quantity  of 
basalt  in  either  of  these  Buttes  is  practically  unlimited  and  the  material 
as  good  as  the  best.  About  two  and  one-half  miles  north  of  Brownsville 
some  good  outcrops  of  basalt  are  found  and  excellent  quarry  sites 
could  be  selected.  On  a butte  situated  two  miles  south  of  the  town  of 
Twin  Buttes  just  east  of  the  railroad  track  is  another  excellent  quarry 
site.  It  is  close  to  and  above  the  railroad  so  the  rock  could  be  handled 
conveniently  by  railroad  transportation.  The  material  is  the  same  hard, 
dense  basalt  exhibiting  the  columnar  structure  of  the  rock  in  Kees 
Butte.  Undoubtedly  similar  outcrops  would  be  found  in  the  foothills 
from  this  point  south  of  the  county  line  but  a detailed  examination  was 
not  made  in  this  section. 

MARION  COUNTY. 

. .Marion  County  has  a large  amount  of  excellent  rocks  for  road  building 
purposes  and  they  are  fairly  well  distributed.  The  southwestern  part  of 
the  county  being  the  most  fortunate  in  this  respect.  The  area  south 
from  Salem  and  west  of  the  Southern  Pacific  railroad  probably  has  a 
better  distribution  of  good  hard,  dense,  black  basalt  than  any  other 
equal  area  in  the  Willamette  Valley,  there  being  very  few  square  miles 
in  this  area  in  which  a good  quarry  site  could  not  be  found.  There 
have  already  been  opened  up  twelve  quarries  in  this  area  and  samples 
taken  from  them  show  a remarkable  uniformity  in  the  type  texture  and 
quality  of  the  rocks.  These  basalts  are  all  very  dense,  hard,  tough 
varieties,  which  from  the  laboratory  test  as  well  as  practical  service 
on  the  roads  have  proven  excellent  for  road  materials.  On  account  of 
the  uniformity  in  the  quality  of  these  materials  it  will  not  be  necessary 
to  discuss  them  separately. 

The  most  noted  quarry  in  this  area  is  the  Ewald  quarry,  two  and 
one-half  miles  south  of  Salem.  The  mass  of  rock  is  unique  in  one 
respect,  namely  on  account  of  its  being  profusely  fissured.  Incipient 
fractures  ramify  the  mass  to  such  an  extent  one  would  have  difficulty 
in  finding  a solid  piece  larger  than  a man’s  head.  On  this  account  it 
aids  materially  in  quarrying,  doing  away  with  the  expense  of  sledging 
the  material  before  being  handled  by  the  crusher.  Fig.  7 shows  the 
appearance  of  the  rock  in  the  face  of  the  quarry  giving  some  idea  of 


38 


the  fissured  condition.  Fig.  8 shows  a general  view  of  this  quarry. 
This  same  material  which  is  found  in  the  Ewald  quarry,  outcrops  on  what 
is  known  as  the  Creek  Canyon  on  the  Cunningham  place  two  miles 
southwest  from  the  Ewald  quarry.  The  same  material  is  found  three 
miles  southwest  from  Salem  outcropping  on  the  river  road.  This  would 
make  an  excellent  site  for  a quarry.  The  Poyser  quarry  seven  miles 
soutnwest  from  Salem  and  two  miles  northwest  from  Independence 
is  an  excellent  quarry  site  on  account  of  being  so  favorably  situated  with 
reference  to  transportation,  being  on  the  county  road  on  the  east  bank 
of  the  Willamette  river.  The  Lankford  quarry  is  located  four  miles 
southwest  from  Salem  on  the  Croisan  Creek  road,  one  and  one-half 
miles  up  the  creek  from  the  river  road.  Numerous  outcrops  of  the  same 
material  are  found  further  south  along  the  Crosian  Creek  Canyon,  the 
Davidson  quarry  seven  and  one-half  miles  southwest  from  Salem  being 
at  the  head  of  Croisan  Creek  about  five  miles  east  from  Independence. 
The  Gilbert  quarry  one-half  mile  west  from  Rosedale,  is  a good  quarry 
site.  The  mass  is  well  fissured  and  broken  up.  The  Rosedale  Quarry  is 
located  one  and  one-fourth  miles  south  from  Rosedale  near  the  southeast 
corner  of  the  R.  C.  Jory  farm  and  one-half  mile  east  of  tue  Kosedaie 
road.  The  Feeble  Minded  Institution  quarry  one  and  one-half  miles  east 
from  the  Davidson  quarry  is  of  the  same  dense,  hard  basalt.  An  exten- 
sive outcrop  of  basalt  is  found  one-half  mile  northwest  from  Turner  on 
the  east  side  of  the  hill.  This  would  be  an  excellent  site  to  obtain  a 
large  quantity  of  rock  as  there  would  be  very  little  stripping  and  a 
quarry  face  could  soon  be  developed  here  75  to  100  feet  high.  Numerous 
outcrops  of  similar  material  are  found  in  the  hills  south  from  Turner  to 
Marion.  Also  on  east  side  of  the  Southern  Pacific  Railway  from  Turner 
north  to  the  Asylum  farm. 

In  the  vicinity  of  Silverton  there  are  numerous  outcrops  of  basalt. 
The  hill  just  east  of  the  town  is  made  up  of  basalt  obscured  by  a few 
feet  of  soil.  Farther  to  the  northeast  from  Silverton  the  hills  are 
mostly  basalt.  The  Morley  quarry  four  miles  northeast  from  Silverton 
is  an  excellent  quarry  site. 

In  the  neighborhood  of  Scotts  Mills  are  found  some  excellent  outcrops 
of  basalt  especially  in  the  canyon  of  Butte  Creek  south  from  the  town. 
These  masses  are  as  good  as  the  best  in  quality,  but  will  be  somewhat 
harder  to  quarry  on  account  of  the  lack  of  fracturing  or  fissuring  which 
is  found  elsewhere.  The  Whitlock  quarry  one  mile  northwest  from 
Scott’s  Mills  is  very  similar  to  the  Morley  quarry  but  is  not  so  good 
a quarry  site  on  account  of  being  too  near  the  creek  level. 

The  butte  known  as  Mt.  Angel  is  one  huge  mass  of  basalt.  The  Mt. 
Angel  quarry  is  located  on  the  southwest  side  of  the  butte  well  up 
toward  the  summit.  The  rock  where  the  quarry  is  opened  is  the  same 
profusely  fissured  basalt  as  before  described  in  the  Ewald  quarry. 
The  basalt  in  this  butte  varies  considerably  in  its  density.  The  outcrops 
in  some  portions  being  very  porous.  This  is  especially  true  farther 
toward  the  summit  near  Mt.  Angel  College.  The  writer  would  suggest 


39 


that  a quarry  just  as  good  as  the  present  road  rock  quarry  could  be 
opened  up  farther  down  the  southwest  slope  of  the  hill  and  thus  be 
more  available  from  tne  road  as  weii  as  save  considerable  time  and 
expense  climbing  the  hill  to  the  present  quarry. 

In  the  extreme  north  side  of  the  county  there  are  some  excellent 
outcrops  of  basalt  southwest  from  Butteville.  On  the  old  Mathoit  place 
three-quarters  of  a mile  southwest  from  Butteville  is  a prominent  butte 
of  basalt  The  north  side  of  the  butte  slopes  down  to  the  Willamette 
river  very  steeply  and  exposes  the  basalt.  This  is  an  excellent  site  for 
a quarry  as  a large  working  face  could  be  quickly  and  easily  opened 
up.  The  material  is  hard,  black  basalt  very  similar  to  that  found  in 
the  Tualatin  hills  across  the  Willamette  river  in  Yamhill  County  in  the 
vicinity  of  Newberg.  Similar  outcrops  of  basalt  are  found  one-half  mile 
farther  southwest  on  the  Tong  Lee  place. 

In  northern  Marion  County  there  is  an  area  of  over  200  square  miles 
between  Mt.  Angel  and  Silverton  on  the  east,  the  Willamette  river  on 
the  west  and  north,  and  Salem  on  the  south  in  which  there  are  found 
no  available  outcrops  of  road  materials.  The  deposit  of  the  Willamette 
river  gravel  on  the  west  and  north  are  available,  however,  and  together 
with  the  outcrops  already  mentioned  on  the  boundary  of  this  area  will 
supply  it  reasonably  well. 

MULTNOMAH  COUNTY. 

Multnomah  county  has  a large  amount  of  the  fine  grained  basic  igneous 
or  trap  rocks  which  are  excellent  materials  for  road  building,  however, 
these  materials  are  not  so  well  distributed  over  the  county  as  in  the 
case  of  some  of  the  other  Willamette  Valley  counties.  The  western 
part  of  the  county  is  well  supplied,  and  again  we  find  plenty  of  road 
material  in  the  eastern  part  of  the  county,  but  a large  area  in  the 
central  part,  extending  from  Rocky  and  Kelly  Buttes  east  to  the  Sandy 
river  has  no  good  road  material  except  gravel. 

On  the  west  bank  of  the  Willamette  river  extending  from  Oswego  to 
Multnomah’s  north  county  line  outcrops  of  basalt  are  found  in  all  the 
canyons  which  cut  the  east  slope  of  the  highland.  In  some  of  these 
canyons  extensive  sections  are  exposed  showing  that  this  material  has 
been  deposited  in  a number  of  successive  lava  flows.  These  different 
outcrops  are  quite  uniform  in  quality,  being  hard,  black,  dense  basalt. 
The  only  exception  being  now  and  then  a layer  of  cellular  basalt,  which 
being  more  or  less  porous,  lacks  in  power  to  withstand  abrasion.  In 
some  of  these  quarries  the  material  shows  considerable  weathering  in 
certain  places  in  the  quarry  owing  to  the  fact  that  under  ground  waters 
have  penetrated  deeper  in  these  places.  A limited  amount  of  this 
weathered  material  for  macadam  purposes  is  no  disadvantage,  but  as 
we  have  already  noted,  a positive  advantage  on  occount  of  the  additional 
binding  power  resulting  therefrom  due  to  the  larger  percentage  of 
screenings  produced.  It  is  very  seldom  in  any  rock  that  sufficient 
screenings  are  produced  to  bind  the  coarser  materials  and  from  exper- 


40 


ience  this  weathered  rock  is  found  to  he  excellent  as  a binding  material. 
Samples  of  rock  taken  from  Linton  quarry  one  and  one-half  miles 
east  of  Linton,  Canyon  quarry  one-half  mile  north  of  Council  Crest, 
Markham  Gulch,  Jackson  Canyon  just  west  of  the  City  Park,  Tanner’s 
Creek  and  Fulton’s  quarry  are  very  similar  and  give  excellent  tests  for 
road  materials. 

Three  miles  west  of  Portland  on  the  Cornell  road  is  a quarry  of 
dense  black  basalt  very  similar  to  that  found  in  above  mentioned 
quarries.  Council  Crest  quarry  is  located  on  the  west  slope  of  Council 
Crest.  The  rock  found  in  this  quarry  is  gray  in  color  and  somewhat 
more  porous  than  the  darker  basalt.  This  rock  is  more  nearly  an 
andesite  than  a basalt  and  on  account  of  its  less  dense  nature  gives  a 
higher  percentage  of  wear  by  abrasion.  It  is  somewhat  inferior  to  the 


Plate;  io. — County  prisoners  at  work.  Kelly  Butte  quarry, 
Multnomah  county. 

black  basalts  as  a road  material  but  gives  good  wear.  Some  outcrops  of 
this  same  andesite  are  found  one  mile  west  of  Council  Crest.  This 
would  make  a good  quarry  site  as  there  seems  to  be  an  almost  unlimited 
amount  of  material.  Pointer’s  Butte  one  and  one-half  miles  farther 
northwest  is  of  the  same  material.  Quarries  might  be  opened  here  to 
accommodate  areas  in  both  Washington  and  Multnomah  counties. 
Taylor’s  Ferry  quarry  contains  an  excellent  quality  of  dense,  black 
basalt. 

On  the  east  side  of  the  Willamette  river  available  outcrops  of  rock 
are  found  at  Kelly’s  Butte  and  Rocky  Butte.  The  material  in  these 
buttes  are  somewhat  similar,  Kelly’s  Butte  being  considerably  finer 
grained.  These  rocks  might  be  classified  andesite  also,  but  are  some- 


41 

times  known  as  gray  basalts.  The  Rocky  Butte  rock  is  very  similar  to 
the  outcrop  west  of  Couiicil  Crest  as  well  as  a number  of  outcrops  in 
Northern  Clackamas  County  near  Baker’s  Bridge  and  all  through  the 
Redland  country.  These  rocks  in  quality  are  somewhat  inferior  to  the 
best  basalts  but  make  good  road  materials.  They  are  not  as  well  adapted 
for  heavy  traffic  as  the  dark,  dense  basalts.  They  are  . considerably 
coarser  grained,  have  smaller  percent  of  the  pyroxenes  and  are  made 
somewhat  porous  to  considerable  depth  by  the  weathering  effect  of 
under  ground  waters.  The  great  depth  to  which  the  first  stages  of  this 
weathering  action  takes  place  can  be  noted  in  the  Kelly  Butte  quarry 
where  at  a depth  of  40  to  50  feet  below  the  surface  the  large  fissure 
blocks  show  the  gradation  from  the  gray  to  the  darker  colored  basalt, 
the  dark  being  considerably  harder  than  the  gray.  The  Kelly  Butte 
rock  is  good  material  however  on  account  of  its  fine  grained  texture 
and  withstands  abrasion  nearly  as  well  as  the  black,  dense  varieties. 

Just  east  of  the  Sandy  river  at  Troutdale  is  an  exposure  of  gray 
basalt  very  similar  to  that  found  in  Rocky  Butte.  This  is  an  excellent 
quarry  site  as  the  material  can  be  easily  handled  and  transported  by 
rail.  From  this  point  up  the  Columbia  river  there  is  a continuous  ledge 
of  basalt  reaching  through  the  county,  showing  an  exposure  very  nearly 
vertical,  and  varying  in  height  from  50  to  200  feet,  see  Fig.  9.  A large 
part  of  this  mass  is  excellent  road  material  but  is  more  available  from 
the  railroad  at  the  foot  of  the  bluff  than  from  the  highlands  above. 
Very  few  outcrops  of  this  basalt  are  found  on  these  highlands  because 
they  are  covered  with  a considerable  depth  of  soil.  About  three  miles 
east  of  Gage  in  the  creek  canyons  a number  of  outcrops  of  basalt  similar 
to  the  Rocky  Butte  material  are  exposed.  These  will  doubtless  furnish 
good  quarry  sites  accommodating  a large  area  in  this  section. 

POLK  COUNTY. 

Polk  County  is  not  as  well  supplied  with  available  outcrops  of  road 
material  as  are  some  of  the  other  counties  in  the  valley.  However  a 
number  of  good  quarries  have  been  opened  and  a number  of  outcrops 
located  which  will  be  of  great  service  to  the  road  builder.  In  the 
vicinity  west  from  Dallas  the  hills  contain  some  outcrops  of  basalt  of 
excellent  quality.  The  two  quarries  from  which  the  rock  for  the  city 
has  been  obtained,  one  three  miles  west  and  the  other  two  miles  west 
and  one  mile  north,  show  very  fine  grained,  black,  dense  varieties  of 
basalt  which  are  as  good  in  quality  as  any  to  be  found  in  the  valley. 
Four  and  one-half  miles  north  and  one  mile  west  of  Dallas  is  another 
excellent  basalt  quarry.  The  mass  of  rock  is  profusely  fissured  similar 
to  that  found  in  the  Ewald  quarry  near  Salem  and  because  of  the 
fissures  is  more  easily  quarried  than  it  would  be  otherwise. 

Four  miles  southwest  of  Dallas  are  located  some  limestone  quarries 
which  were  recently  purchased  by  the  Oswego  Cement  Company  of 
Portland.  This  rock  seems  to  be  very  popular  in  this  section  as  a road 
material,  largely  on  account  of  the  fact  that  it  is  easly  quarried  and 


42 


crushed  and  works  down  quickly  into  a good  road  without  being  rolled. 
From  this  standpoint  it  certainly  is  a good  rock  for  road  material  but 
cannot  be  recommended  for  use  alone  for  building  the  best  macadam 
roads.  Under  heavy  traffic  the  surface  of  the  road  will  be  found  to 
wear  rapidly  and  will  need  constant  repair,  as  the  rock  is  not  hard 
enough  to  sufficiently  withstand  the  abrasion  of  heavy  traffic.  This 
rock  used  as  a binder  for  a harder  trap  rock  would  make  excellent 
macadam  roads,  which  would  give  the  best  of  satisfaction.  Just  west 
of  the  town  of  Falls  City  is  a quarry  in  coarse  grained  diabase.  This  is 
a tough,  hard  rock  and  gives  good  tests  as  a road  material.  Four  miles 
southeast  of  Falls  City  is  a quarry  the  rock  being  the  same  as  that  of 
the  Falls  City  quarry.  In  the  vicinity  of  Multnomah  some  basalt  quarries 
could  probably  be  opened  up  by  making  careful  search  as  is  evidenced 
by  the  fact  that  basalt  boulders  are  found  strewn  over  the  hillsides  in 
this  vicinity. 

Polk  County  has  large  areas  which  apparently  have  no  available  road 
material.  On  this  account  it  will  be  necessary  to  depend  largely  upon 
the  Willamette  river  gravels  for  economic  materials.  By  crushing  and 
transporting  by  rail  these  gravels  can  be  readily  distributed  to  nearly 
all  parts  of  the  county. 


TILLAMOOK  COUNTY. 

Although  Tillamook  County  is  not  located  in  the  Willamette  Valley,  it 
is  included  in  this  bulletin  because  of  the  great  demand  for  investigation 
of  the  materials  in  this  section.  This  county  has  done  a great  deal 
of  work  in  building  up  to  date  roads  and  deserves  credit  for  the  result 
obtained. 

Tillamook  County  has  a greater  variety  of  rocks  than  any  of  the 
Willamette  Valley  counties  and  as  might  be  expected  their  qualifications 
for  road  making  are  just  as  varied.  About  five  miles  southeast  from 
Tillamook  city  near  the  Red  Clover  cheese  factory  on  the  Trask  river 
is  found  an  outcrop  of  rhyolite  tuff  which  appears  on  the  map  as  sand- 
stone. This  material  is  formed  by  an  accumulation  of  volcanic  fragments 
more  or  less  cemented  together  and  on  the  whole  makes  rather  poor 
macadam  material.  Aside  from  the  fact  that  it  is  easily  ground  up 
under  traffic  it  seems  to  slack  on  exposure  to  the  weather  and  although 
it  rolls  down  and  makes  a good,  smooth  macadam  road  quickly  it  has 
not  sufficient  stablility  to  withstand  the  ordinary  traffic,  on  this  account 
it  is  not  an  economical  material  for  use  if  any  other  material  is  available. 
A good  trap  rock  is  found  about  a mile  farther  up  the  Trask  river  which 
could  be  used  to  a better  advantage  on  the  roads  in  this  vicinity.  The 
rock  in  the  neighborhood  of  Bester’s  Ford  five  miles  east  from  Tillamook 
is  mostly  sandstone  and  conglomerate.  This  particular  sandstone  is 
entirely  unfit  for  macadam  material  as  it  is  rather  poorly  cemented 
argillaceous  sandstone.  In  these  the  sand  grains  are  cemented  together 
with  a sort  of  clay  material  on  the  whole  making  quite  a friable  rock. 
A conglomerate  or  “cement  rock”,  as  it  is  sometimes  called,  is  found 


43 


near  the  stream  bed  at  this  point.  It  contains  a large  amount  of  good  trap 
rock  but  is  not  well  situated  for  economic  handling.  About  one  and  a 
half  miles  farther  up  the  stream  there  are  outcrops  of  basalt  porphyry 
which  will  make  excellent  road  material. 

In  the  vicinity  of  Beaver  south  from  Tillamook  is  quite  an  extensive 
outcrop  of  shaly  limestone.  This  rock  has  been  quarried  quite  extensively 
and  the  material  has  been  used  for  a number  of  miles  of  road  in  this 
section.  This  rock  makes  a fair  material  for  macadam  purposes,  it  being 
easily  smoothed  down  into  a good  surface.  It  has  an  excellent  binding 
effect  due  to  the  fact  that  it  is  comparatively  easily  ground  up  under 
traffic  and  gives  a considerable  amount  of  finer  material  which  as 
we  have  already  found  always  aids  in  the  bonding  action.  Under  heavy 
traffic  roads  made  from  this  material  will  be  found  to  wear  quite  rapidly 
and  if  a harder  rock  could  be  used  with  this  material  as  a binder  it  would 
give  better  results.  There  is  a considerable  amount  of  gravels 
in  the  streams  in  this  section  which  is  largely  made  up  of  good,  hard 
trap  rock  and  might  be  used  to  good  advantage. 

Still  farther  south  in  the  neighborhood  between  Hebo  and  Castle 
Rock  are  found  numerous  outcrops  of  good,  hard,  rather  coarse  grained 
igneous  rock,  diabase.  There  are  unlimited  quantities  of  this  material 
in  this  section  and  will  make  good  road  material.  It  is  composed  of 
about  45  per  cent  feldspar  and  averages  about  30  per  cent  pyroxene, 
making  on  the  whole  rather  a tough,  hard  rock  which  will  withstand 
abrasion  well.  The  same  rock  but  finer  grained,  more  on  the  order  of 
basalt,  is  found  as  you  approach  Hebo  from  Castle  Rock,  it  being  more 
coarse  grained  in  the  vicinity  of  Castle  Rock.  On  the  Clover  Dale  road, 
southwest  from  Hebo  there  is  found  an  outcrop  about  one  mile  east 
from  Clover  Dale  in  a cut  in  the  road  side,  an  excellent  hard,  dense 
Basalt.  This  rock  is  favorably  located.  A quarry  might  be  easily  opened 
at  this  point  and  accommodate  a large  section  in  this  vicinity. 

An  outcrop  of  excellent  hard,  dense  basalt  is  also  found  close  to 
Pacific  City  which  will  be  excellent  for  road  material  and  can  be  used 
to  accommodate  a large  area  in  this  neighborhood.  A very  large  amount 
of  basalt  porphyry  is  found  in  the  vicinity  of  Estella  Falls,  two  miles 
southeast  from  the  junction  of  the  Ore  Town  road  with  the  Estella 
Falls  road.  This  is  excellent  material  and  is  found  in  unlimited 
quantities  and  may  be  of  considerable  use  in  the  near  future  as  a road 
building  rock.  Good  hard  basalt  is  also  found  in  the  vicinity  of  Neskowin. 
The  main  outcrops  being  found  one  and  one-half  miles  north  from 
Neskowin.  This  is  excellent  hard,  tough  material  and  should  be  of  very 
great  service  to  this  community,  as  a road  rock. 

North  from  Tillamook  City  in  the  vicinity  of  Hobsonville  on  the  north 
side  of  .Tillamook  Bay,  there  is  a point  known  as  Miami  quarry.  Here 
is  found  a more  or  less  weathered  diabase.  In  this  rock  the  pyroxenes 
are  largely  changed  to  cholorite  making  the  rock  considerably  softer 
than  it  was  originally,  however,  the  rock  is  quite  firm  and  gives  fairly 
good  results  from  the  standpoint  of  abrasion  and  is  probably  the  best 


Plate  ii. — Macadam  road  construction 


45 


rock  for  road  material  which,  could  be  found  in  this  vicinity.  It  is  very 
accessible  to  transportation  being  situated  upon  the  railroad  and  on  this 
account  will  probably  be  of  great  service  to  a considerable  portion  of 
Tillamook  County.  This  same  rock  outcrops  just  above  the  town  of 
Hobsonville  but  seems  to  be  much  sotter  than  in  the  Miami  quarry.  The 
examination  was  made  entirely  upon  the  surface  material  and  it  is 
probably  that  a quarry  might  be  opened  up  there  in  which  the  material 
would  compare  very  favorably  with  the  Miami  quarry. 

In  the  northern  part  of  the  county  in  the  neighborhood  of  Nehalem 
bay  at  a point  on  the  south  side  or  the  mouth  of  the  Nehalem  river  in 
the  railroad  cut  there  is  exposed  an  outcrop  of  fresh,  hard,  dense 
diabase,  made  up  largely  of  feldspar  and  a goodly  percent  of  pyroxene, 
an  excellent  material  for  road  purposes.  This  material  is  favorably 
situated  there  being  a large  amount  of  material  in  sight  and  also  upon 
the  railroad.  This  same  hard  diabase,  is  found  on  Coal  Creek  about  one 
and  one-fourth  miles  above  the  bridge  across  North  fork  of  the  Nehalem 
river.  This  would  make  an  excellent  quarry  site.  Another  outcrop  of 
the  same  material  is  found  on  the  north  fork  of  the  Nehalem  road  about 
one-eighth  of  a mile  northeast  from  the  main  road  from  Tillamook  to 
Nehalem.  This  material  is  almost  identical  with  the  two  previously 
mentioned.  The  supply  of  the  latter  two  are  probably  unlimited. 

There  are  certain  areas  in  Tillamook  County  which  are  situated  at 
a considerable  distance  from  these  favorable  outcrops  of  good  material, 
which  will  have  to  rely  upon  the  river  gravels  for  road  materials,  as 
there  seems  to  be  no  available  rocks  of  good  quality  near  enough  to  be 
of  service. 

WASHINGTON  COUNTY. 

Washington  County  does  not  have  its  road  materials  as  well  dis- 
tributed as  some  of  the  valley  counties.  The  soils  have  accumulated  to 
such  a great  depth  over  a large  part  of  the  county  that  outcrops  are 
very  few  and  far  between.  When  the  rocks  are  exposed  in  some  creek 
canyon,  if  quarried  for  a short  distance  require  such  a large  amount 
of  stripping  that  it  is  very  expensive.  Two  miles  west  of  Gaston  is  an 
outcrop  of  sandstone  which  has  been  used  to  some  extent  in  taht 
neighborhood  as  road  material.  Although  this  material  gives  fair  results 
its  use  would  not  be  warranted  if  other  material  could  be  procured. 
Near  Dilley  an  outcrop  of  basalt  of  excellent  quality  is  found.  The 
quarry  site  is  rather  poor,  however,  and  only  a limited  amount  of  rock 
can  be  obtained  without  lowering  the  quarry  floor.  The  Thatcher  quarry, 
situated  about  three  miles  northwest  of  Forest  Grove  is  excellent  dense, 
hard  basalt.  The  only  objectionable  feature  in  the  quarry  is  the  great 
amount  of  over  burden  which  requires  stripping  as  fast  as  the  rock  face 
is  quarried. 

In  the  extreme  southeastern  part  of  the  county  are  the  most  important 
outcrops  of  trap  rock  found.  About  five  miles  southeast  of  Hillsboro 
are  some  outcrops  of  basalt  and  although  no  extensive  quarries  have 


46 


been  opened  up,  good  quarries  can  without  doubt  be  located  here  with 
a comparative  small  amount  of  stripping.  Farther  to  the  southeast  are 
a number  of  good  basalt  outcrops,  the  most  important  being  in  the 
neighborhood  of  Tonquin  on  the  Oregon  Electric  Railway.  One-fourth 
of  a mile  north  of  'the  station  is  an  excellent  location  for  a quarry,  and 
it  is  very  probable  that  a large  part  of  Washington  County  can  be  accom- 
modated from  this  point.  Just  east  of  Tualatin  near  the  Southern 
Pacific  Railroad  is  another  good  quarry  site  from  which  considerable 
material  might  be  distributed.  Just  east  of  the  station  at  Tigard  is  a 
good  outcrop  of  porphyritic  material  which  will  make  excellent  road 
material.  The  tunnel  which  is  being  driven  in  the  neighbrohood  of 
Phillips  has  passed  through  good,  dense  basalt  for  950  feet  and  it  is 
possible  that  some  favorable  localities  might  be  found  in  this  vicinity 
for  quarries. 

YAMHILL  COUNTY. 

Yamhill  County  is  more  fortunately  situated  with  reference  to  good 
road  building  rocks  than  either  Washington  or  Polk.  There  are  a 
number  of  good  trap  rocks  well  distributed  over  the  county.  The 
Willamette  river  gravels  are  available  along  the  southeast  boundary  line 
and  will  accommodate  a considerable  area  tributary  to  it. 

One-half  mile  north  of  the  town  of  Amity  is  an  outcrop  of  hard,  dense 
basalt  very  profusely  fissured  and  broken  up  similar  to  the  Ewald 
quarry  south  of  Salem,  making  the  rock  easier  to  quarry  than  it  other- 
wise would  be.  From  this  point  northeast  for  a distance  of  four  or  five 
miles,  is  a range  of  hills  in  which  indications  are  that  numerous  outcrops 
could  be  found.  A quarry  is  located  four  miles  east  of  Whiteson  at  the 
extreme  northeast  point  of  this  range.  The  rock  in  this  quarry  is 
identical  in  every  respect  with  that  found  in  the  Amity  quarry.  This 
rock  gives  excellent  tests  as  a road  metal.  About  three-fourths  of  a 
mile  southwest  of  Bellevue  is  a quarry  of  altered  basalt.  This  rock 
is  considerably  softer  than  the  average  basalt  and  on  account  of  a 
great  amount  of  secondary  calcite  being  developed  in  it,  it  is  shown 
on  the  map  accompanying  this  bulletin  as  limestone.  This  rock  will 
make  a good  road  where  the  traffic  is  not  too  severe.  If  required  for 
a road  which  has  a great  amount  of  heavy  travel  it  would  be  good  policy 
to  select  a harder  rock  for  the  main  mass  of  the  road  and  use  this 
rock  as  a binder. 

About  three  miles  northwest  of  Bridewell  on  a prominent  point  of 
hills  is  found  a good  outcrop  of  hard,  dense  basalt,  which  would  make 
an  excellent  quarry  site.  The  McMinnville  quarry  west  of  the  city 
exposes  a face  of  fine  dense  black  basalt  which  will  make  as  good  road 
material  as  can  be  found  anywhere.  An  outcrop  of  diorite  is  found  at 
a point  about  five  miles  northwest  of  McMinville  near  Dawson  Creek. 
This  rock  is  coarse  grained  and  although  it  does  not  give  as  good  tests 
for  road  material  as  the  fine  grained  basic  rocks  it  is  well  adapted  for 
the  construction  of  roads  and  should  give  good  service.  About  two  and 
one-half  miles  west  of  Carlton  are  found  a couple  of  quarries  of  good. 


47 


hard,  tough  diabase  which  make  excellent  material  for  macadam  pur- 
poses. About  two  and  one-half  miles  west  of  Yamhill  is  another  outcrop 
of  diabase  very  similar  to  the  quarries  west  of  Carlton.  These  should 
do  good  service  in  this  vicinity  in  supplying  road  materials.  Two  miles 
north  of  Lafayette  are  found  some  excellent  quarries  showing  dense 
black  basalt.  This  rock  is  considerably  fissured,  similar  to  that  in  the 
Amity  quarry  before  mentioned.  Three  miles  west  of  Newberg  is  a hill 
upon  which  are  found  outcrops  of  dense,  fine  grained  basalt.  A quarry 
is  opened  up  on  the  southwest  side  of  the  bill  and  shows  somewhat  the 
same  fissured  structure  found  in  the  Amity  and  Lafayette  quarries. 
About  one  mile  north  and  one-half  mile  east  of  Newberg  is  a quarry  of 
the  same  dense,  hard  basalt.  It  is  an  excellent  site  where  a large 
amount  of  rock  may  be  obtained,  and  is  especially  desirable  since  it  is 
close  to  the  railroad.  Just  south  of  the  town  of  Newberg  across  the 
creek  on  the  road  to  Dayton,  is  found  an  outcrop  of  good,  hard  quality 
basalt.  It  is  not  however  a good  quarry  site  for  obtaining  a large 
amount  of  rock. 

SUGGESTIONS  FOR  SELECTING  A QUARRY  SITE. 

A few  suggestions  as  to  important  points  to  be  observed  in  the 
intelligent  selection  of  quarry  sites  may  be  of  assistance  to  the  road 
builder.  Careful  preliminary  examination  before  selecting  a site  for 
the  quarry  cannot  be  too  strongly  emphasized,  because  the  expense  of 
several  days  or  weeks  of  careful  prospecting  will  often  be  offset  by  a 
single  days  expense  in  needlessly  stripping  a heavy  overburden  in  an 
unfavorable  location,  or  by  a single  days  expense  in  extra  hauling. 
With  all  due  respect  to  the  road  builders,  in  a number  of  localities  over 
the  Willamette  Valley  the  counties  are  paying  a heavy  tax  of  incom- 
petency or  lack  of  careful  preliminary  examination  before  selecting  the 
most  advantageous  point  for  the  location  of  the  quarry.  In  this  con- 
nection it  should  be  stated  that  no  county  or  community  which  is 
contemplating  any  considerable  amount  of  road  building  can  invest  their 
funds  in  a way  that  will  bring  greater  results  than  in  intelligent 
engineering  management.  Very  few  people  seem  to  understand  thq 
duties  or  office  of  the  road  engineer. 

The  engineering  department  of  the  Oregon  Agricultural  College  is 
pursuing  as  a policy,  the  belief  that  the  road  engineer  should  not  only 
be  thoroughly  familar  with  the  details  of  surveying,  draining,  grading 
and  general  construction,  but  he  should  also  be  able  to  go  into  the  field 
and  intelligently  select  all  the  most  available  quarry  sites  which  will 
give  good  road  materials,  and  to  manage  all  the  details  of  the  work 
with  best  financial  results.  To  do  this  he  must  be  able  to  determine  the 
extent  of  the  different  rock  ledges,  their  adaptability  for  road  metal,  to 
estimate  accurately  the  comparative  cost  of  opening  up  quarries  at 
different  points  in  a community,  to  intelligently  plan  the  equipment  of 
quarrying  and  crushing  plants,  to  estimate  the  cost  of  quarrying, 
crushing  and  hauling,  and  in  view  of  all  the  above  details  to  prosecute 


PivATE  12. — Good  rural  schools  and  good  roads  go  hand  in  hand.  Marion  County. 


49 


the  work  in  an  efficient  manner  and  ultimately  obtain  from  it  the  most 
economical  results.  This  evidently  can  only  be  accomplished  by  employ- 
ing the  trained  experienced  highway  engineer  and  giving  him  full  charge 
of  the  work,  unhampered  by  lack  of  funds. 

We  would  not  attempt  here  to  give  all  the  details  of  intelligent  selec- 
tion of  quarry  sites,  for  as  has  already  been  intimated,  this  includes  a 
large  proportion  of  the  road  engineer’s  training  and  can  only  be  attained 
by  a careful  study  of  some  of  the  fundamentals  of  the  principles  of 
geology.  We  can,  however,  give  some  useful  suggestions  which  should 
be  of  service  to  the  people  who  are  now  doing  the  road  building. 

In  the  discussion  of  the  general  geology  of  the  Willamette  Valley  it 
has  already  been  noted  that  the  south  or  west  slopes  of  hills  usually 
have  a less  depth  of  soil  and  therefore  more  outcrops  of  fresh  rock  than 
the  east  and  north  sides,  for  the  reason  that  the  wind  has  a better 
chance  at  these  slopes  and  carries  the  soil  away  as  fast  as  formed.  For 
this  reason  more  numerous  outcrops  are  found  in  the  first  foot  hills 
on  the  east  side  of  the  valley  than  the  corresponding  ones  on  the  west 
side  of  the  valley.  In  almost  every  case  the  south  or  west  slopes  of 
hills  will  be  found  most  advantageous  for  quarry  sites.  The  exceptions 
to  this  statement  being  where  stream  erosion  exposes  the  north  or  east 
sides  of  the  hills.  It  should  be  borne  in  mind  that  canyons  are  almost 
always  formed  by  the  erosion  of  the  streams  which  occupy  them,  hence 
outcrops  may  be  expected  upon  the  sides  of  stream  canyons.  In  general, 
the  steeper  the  canyon  side  the  less  the  depth  of  soil.  Very  often  the 
rock,  when  covered  by  soil  upon  the  canyon  side,  will  be  found  freshly 
exposed  in  the  stream  bed,  thus  giving  a clue  to  the  grade  of  material 
which  could  be  opened  up  in  a quarry  on  the  canyon  side. 

On  account  of  the  necessary  expense  in  opening  and  installing  equip- 
ment at  a quarry  it  is  probable  that  quarries  will  not  usually  be  located 
closer  to  each  other  than  two  miles,  even  if  a number  of  available 
quarry  sites  should  be  found.  On  the  other  hand,  it  will  be  found  that 
in  most  cases  five  or  six  miles  will  be  the  maximum  distance  between 
quarries  where  outcrops  are  available,  because  the  expense  of  haul 
with  teams  will  be  sufficient  to  warrant  the  expense  of  opening  and 
equipping  a new  quarry.  Other  means  of  mechanical  transportation 
such  as  railroad  or  auto  trucks  will  of  course  vary  this  maximum  limit. 

The  principles  of  rock  weathering  are  very  important  as  an  aid  in 
the  selection  of  a quarry  site.  It  will  not  be  possible  to  give  many 
details  along  this  line  here,  but  some  useful  hints  may  be  given.  A 
large  proportion  of  the  low  hill  lands  in  the  Willamette  Valley  are 
made  up  of  the  basic  igneous  fine  grained  rocks  known  as  trap  or  trap 
rock.  These  rocks  are  rich  in  iron  and  as  they  decay,  this  iron  is 
changed  from  the  original  silicate  to  the  secondary  oxide,  the  natural 
color  of  which  is  red  or  brown.  Thus  the  soils  derived  from  these 
rocks  are  painted  red  or  brown  and  give  rise  to  a large  amount  of  the 
“red  hill  lands”  so  common  in  the  Willamette  Valley.  On  this  account 
then  it  is  usually  easy  to  locate  trap  rock  outcrops,  but  these  outcrops 


50 


are  usually  hidden  by  a greater  or  less  depth  of  soil.  By  applying  some 
of  the  principles  already  mentioned  the  most  favorable  points  upon  the 
hill  can  be  selected. 

It  is  of  the  utmost  importance  in  selecting  the  proper  site  for  the 
quarry  that  the  location  of  the  crushing  plant  be  considered.  If  possible 
the  crusher  should  be  placed  so  that  its  mouth  is  just  below  the  floor 
of  the  quarry  in  order  to  insure  convenience  in  handling  of  material. 
The  writer  has  observed  a number  of  quarries  in  different  parts  of  the 
valley  where  the  material  from  the  quarry  is  wheeled  up  a steep  incline 
and  dumped  upon  a platform  from  which  the  material  is  fed  into  the 
crusher.  This  extra  work  could  have  been  obviated  by  placing  the 
crusher  in  a pit.  Pushing  a car  or  wheelbarrow  load  of  rock  up  an 
incline  is  excellent  exercise  but  not  good  engineering  management.  One 
instance  of  the  location  of  a quarry  may  be  noted  as  a typical  example 
of  poor  management.  The  excavation  was  made  on  one  side  of  the  hill, 
developing  a pit  some  ten  or  twelve  feet  deep.  A road  way  was  main- 
tained down  into  the  pit,  around  to  the  opposite  side  of  the  hill  and  the 
rock  shovelled  from  the  wagons  to  a platform  after  which  it  was  fed 
into  the  crusher.  The  reason  given  for  such  an  arrangement  was  to 
prevent  damage  to  the  crusher  by  blasting  rock  upon  it. 

GRAVELS  Ii\  THE  WILLAMETTE  RIVER. 

The  Willamette  river  with  its  main  tributaries  winding  through  the 
Willamette  Valley  is  without  doubt  the  most  important  good  roads  asset 
that  we  posses.  We  have  already  seen  in  the  description  of  the  general 
geology  of  the  Willamette  Valley  that  the  valley  floor  is  bounded  on 
all  sides  by  foothills  composed  almost  entirely  of  igneous  rocks,  and 
what  is  more  the  best  grade  of  igneous  rocks,  namely  trap  rocks.  Since 
the  gravels  carried  by  any  stream  or  found  upon  its  bed  must  necessarily 
be  derived  from  the  outcrops  of  rock  through  which  it  runs,  it  would 
follow  that  the  gravels  will  always  be  of  the  same  material  as  the  out- 
crops of  rocks  in  place  through  which  the  stream  passes.  For  the 
past  thousands  upon  thousands  of  winters,  the  friendly  old  Willamette 
has  been  carrying  and  rolling  these  fragments  of  rock  along  its  bed 
leaving  in  its  train  an  immense  amount  of  road  material.  On  this 
account  we  have  a continuous  deposit  of  gravel  over  200  miles  in  length 
with  probably  an  average  width  and  depth  of  300  feet  and  6 feet 
respectively,  winding  through  the  central  part  of  the  valley.  In  other 
words,  the  Willamette  riyer  contains  more  road  material  than  would 
be  needed  to  surface  all  the  roads  in  the  state  of  Oregon  15  feet  wide 
and  6 inches  in  depth.  Upon  careful  examination  at  a number  of 
different  points  along  the  Willamette  river  these  gravels  are  found 
to  be  over  90  per  cent  trap  rock. 

These  gravels  in  the  bed  of  a stream  will  vary  considerably  in  size  at 
different  points  in  the  same  stream,  owing  to  the  varying  velocity  of 
the  current  at  different  points.  At  rapid  points  in  the  stream  they 
are  invaribly  many  times  the  average  volume  of  those  in  comparatively 


51 


smooth  portions  of  the  stream.  The  size  of  the  gravel  in  a stream  bed 
varies  also  with  reference  to  its  distance  from  the  head  waters.  This 
is  due  partly  to  the  fact  that  the  velocity  of  the  stream  is  greater  near 
the  head  waters  and  partly  to  the  fact  that  the  individual  gravel  in  the 
stream  near  its  source  have  been  subjected  to  much  less  abrasion  than 
those  farther  down. 

In  the  light  of  the  above  discussion  the  gravels  in  the  Willamette 
river  bed  at  Eugene  are  found  to  be  much  coarser  than  at  Portland, 
also  that  these  gravels  vary  a great  deal  in  size  at  different  points  in 
the  same  locality.  Since  this  gravel  is  over  90  per  cent  trap  rock  how 
about  its  qualifications  for  a road  material?  It  is  a well  known  fact 
among  practical  road  builders  that  gravel  is  not  satisfactory  for  a 
road  surfacing  material  as  crushed  rock  of  good  quality  from  the 
quarry.  The  reason  for  the  difference  between  the  two  as  usually  given, 
is  on  account  of  the  inferior  material  of  the  gravel.  We  have  shown  in 
the  case  of  the  Willamette  river  gravel  that  the  material  is  as  good  as 
the  best,  being  nearly  all  trap  rock,  hence  we  will  have  to  account  for 
the  diffficulty  with  the  gravel  along  other  lines.  This  is  found  in  the 
rounded  shapes  of  the  gravel.  It  lacks  the  wedging  characteristics  that 
the  angular  crushed  rock  possesses,  already  discussed  under  cementing 
or  binding  value  of  rocks.  Clean  rounded  gravel  will  not  pack  or  wedge 
together  like  angular  fragments  of  crushed  rock,  in  fact  any  practical 
road  builder  will  attest  to  the  fact  that  gravel  cannot  be  rolled  with  the 
road  roller  until  some  binding  material  is  added,  such  as  gravel  screen- 
ings or  crushed  rock  screenings,  but  will  push  ahead  of  the  roller  and 
allow  it  to  sink  down  through  the  gravel  mass  by  displacement. 

This  then  is  the  vital  difference  between  a gravel  and  macadam  road; 
one  will  pack  by  virtue  of  the  shape  of  its  angular  fragments  alone, 
while  the  other  depends  entirely  upon  the  binding  material  in  the  voids 
to  make  it  pack  together  into  a good,  firm  road.  A well  made  gravel 
road  is  an  excellent  road,  however,  and  although  it  required  a greater 
thickness  of  gravel  to  support  the  same  load  as  the  crushed  rock  road, 
yet  it  has  sufficient  strength  for  any  ordinary  traffic,  and  gravel  roads 
often  give  practically  as  good  results  as  the  best  of  macadam. 

Again  referring  to  the  coarser  gravels  in  the  Willamette  river  is 
there  any  good  reason  why  these  gravels  cannot  be  dredged  out  of  the 
river,  crushed  and  used  for  building  macadam  roads  in  the  vicinity  of 
the  river?  There  are  numerous  places  along  the  river  where  these 
gravels  will  range  in  size  from  a man’s  fist  to  his  head,  and  if  crushed 
will  be  broken  into  from  5 to  50  nieces  each.  This  material  will  then 
be  equally  as  good  for  macadam  material  as  that  obtained  from  the 
quarry.  This  i?  a very  important  factor  from  the  standpoint  of  economy 
for  two  reasons;  first,  by  reference  to  the  map  showing  distribution  of 
rock  material  it  will  be  seen  at  once  that  there  are  comparatively  few 
outcrops  of  good  road  making  rocks  near  the  river,  but  that  they  are 
located  on  the  first  rim  of  the  foot  hills  bounding  the  valley.  Now 
since  the  river  winds  its  way  approximately  through  the  center  of  the 


PiyATE  13. — Crushing  plant.  Ewald  quarry,  Marion  county. 


53 


valley  it  becomes  the  most  important  factor  in  equalizing  the  distribution 
of  available  materials  in  the  valley.  As  is  pointed  out  in  the  discussion 
of  cost  data,  transportation  is  a very  important  item  in  the  cost  of 
construction  of  the  average  macadam  road.  Secondly,  the  cost  of  pre- 
paring these  coarse  gravels  for  macadam  materials  as  compared  with 
the  cost  of  preparation  of  ledge  rock,  can  be  considerably  reduced.  With 
a reasonably  good  dredging  apparatus  and  good  engineering  management, 
crushed  gravel  can  be  delivered  into  the  wagon  for  at  least  one-half  the 
cost  of  average  condition  in  the  quarry.  Some  road  builders  object  to 
this  added  expense  of  crushing,  and  advocate  using  the  finer  gravel 
screened  without  crushing.  In  answer  to  this  objection  it  should  be 
noted  that  the  additional  expense  of  crushing  is  very  small  and  that  the 
advantages  will  more  than  offset  this  expense.  If  the  work  is  to  be 
quite  extensive  it  will  be  evident  at  once  to  the  experienced  engineer, 
that  in  order  to  screen  and  load  gravel  economically  he  must  provide 
a mechanical  elevator  and  screens  both  operated  by  power,  delivering 
the  gravel  into  bunkers  from  which  it  can  be  delivered  by  gravity 
directly  into  wagons.  Now  by  adding  the  crusher  to  che  equipment  we 
have  not  necessarily  reduced  the  capacity  of  the  plant  and  have  added 
only  a small  additional  expense  in  extra  power  and  repairs.  Tn  return,  if 
coarse  gravel  is  used,  we  get  crushed  rock  as  a product  thereby  reducing 
the  amount  of  material  required  for  the  construction  of  the  road.  We 
are  also  insured  a more  uniform  product,  and  are  relieved  of  the  exoenso 
of  discarding  the  coarse  gravel  which  would  pass  over  the  screens  in 
the  gravel  pla.nl  without  the  crusher.  On  the  whole  the  crusher  in  such 
a plant  will  be  found  quite  an  economical  factor  if  much  gravel  is  to  he 
handled,  and  absolutely  indispensible  where  the  gravel  is  coarse. 

GENERAL  OBSERVATIONS  AND  SUGGESTIONS. 

Among  the  large  number  of  road  builders  in  the  valley,  we  would 
expect  to  find  different  opinions  as  to  the  best  methods  of  road  con- 
struction. It  is  the  purpose  of  the  following  discussion  to  correct  as  far 
as  possible  some  of  the  prevailing  erroneous  ideas  with  reference  to  road 
building.  The  time  has  arrived  in  the  Willamette  Valley  when  we  should 
get  together  and  stand  as  a unit  for  up-to-date,  systematic  building  of 
permanent  roads. 

There  are  a number  of  road  builders  in  the  valley  who  apparently 
are  of  the  opinion  that  a heap  of  gravel  dumped  along  the  middle  of  the 
road  and  driven  over  until  packed  makes  a good  road.  Gravel  roads 
make  good  roads  but  there  is  a right  and  wrong  way  to  construct  them. 
The  road  bed  should  always  be  well  drained,  carefully  prepared  and  the 
subgrade  rolled  and  good  substantial  shoulders  formed.  The  gravel 
should  always  be  screened  and  the  respective  sizes  put  on  separately; 
and  the  whole  mass  rolled  and  well  bound  with  sufficient  binding 
material.  Under  these  conditions  there  will  be  no  more  material  used 
than  in  the  old  fashioned  gravel  road,  while  the  extra  labor  and  ex- 
pense will  be  more  than  offset  by  the  satisfaction  to  be  derived  from 


54 


the  up-to-date  gravel  road. 

It  is  the  practice  in  a number  of  localities  in  the  valley  to  place  a 
quantity  of  uncrushed  rock  on  the  road,  depending  upon  the  traffic  to 
do  the  crushing.  This,  as  anyone  will  testify,  is  an  inconvenient  as  well 
as  expensive  way  of  crushing  rock. 

There  are  communities  in  which  great  pains  are  taken  to  crush  the 
rock  and  to  screen  it  separating  the  different  sizes  after  which  the 
whole  mass  is  usually  laid  upon  a crown  in  the  road,  without  any 
preparation  of  the  road  bed  having  been  made  to  receive  it.  In  this 
method,  traffic  is  again  depended  upon  for  packing  or  consolidating  the 
mass.  The  result  is  that  a large  part  of  the  crushed  rock  is  worked  off 
at  each  side  of  the  road  by  the  traffic,  and  the  central  part  of  the  road 
is  soon  worn  into  ruts.  Although  this  method  is  an  improvement  over 
the  gravel  heaps  or  the  loose  uncrushed  rock  road,  it  is  still  very  un- 
satisfactory. A small  amount  of  additional  funds  invested  in  a road 
roller,  as  well  as  some  attention  paid  to  preliminary  preparation  of  the 
road  bed  to  receive  the  crushed  rock,  would  pay  handsome  dividends  on 
the  investment. 

In  still  other  localities  the  practice  has  been  observed  of  placing  upon 
a well  prepared  road  bed  a foundation  of  a layer  of  larger  rocks.  These 
rocks  are  often  from  eight  to  ten  inches  in  diameter.  Crushed  rock  is 
then  spread  over  the  boulders  and  rolled  in  the  ordinary  way.  This 
method  makes  an  excellent  road,  but  not  an  economical  one,  for  the 
reason  that  almost  twice  as  much  material  as  is  needed  is  used.  It  is 
evident  that  the  boulder  foundation  in  such  a road  contains  an  ample 
amount  of  material,  if  crushed,  to  construct  the  best  of  macadam  roads. 

The  road  equipment  in  some  counties  includes  three  or  four  crushers 
and  one  roller.  The  idea  seems  to  prevail  that  a number  of  crushers  are 
required  to  keep  the  roller  busy.  Under  these  conditions  the  road  rarely 
receives  a sufficient  amount  of  rolling  to  make  it  first  class.  The 
ordinary  size  crusher,  nine  inch  by  fifteen  inch  opening,  if  used  to  its 
capacity  will  furnish  from  sixty  to  seventy-five  cubic  yards  of  crushed 
rock  per  day.  If  the  macadam  road  is  properly  rolled  it  will  be  found 
that  from  three  hundred  to  four  hundred  square  yards  is  all  that  any 
ordinary  size  road  roller  will  be  able  to  complete  in  a day.  If  the 
macadam  is  six  inches  thick  this  makes  from  fifty  to  sixty-five  cubic 
yards.  It  is  evident  that  the  ordinary  crusher  will  keep  a roller  busy. 

It  is  the  practice  of  some  road  builders  to  place  tile  drains  underneath 
the  surfaced  portion  of  the  macadam  road.  This  practice  is  not  only  a 
useless  expense  but  a positive  detriment,  as  the  tile  tends  to  destroy  the 
capillary  action  of  the  water  and  dry  out  the  road  surface,  destroying 
the  binding  action.  This  same  principle  is  often  noted  in  the  surface 
of  macadam  roads  over  a high  fill.  Under  these  conditions  the  surface 
ravels  at  this  point  more  readily  during  the  dry  season  than  in  the  less 
elevated  portions  of  the  road.  If  the  ditches  on  either  side  of  a 
macadam  road  are  ample  in  size  and  grade  to  carry  the  water,  and  are 


55 

from  fifteen  inches  to  eighteen  inches  below  the  crown  of  the  road  the 
sub-grade  will  be  amply  drained. 

Another  very  common  fault  in  road  construction  observed  in  the  valley 
is  a tendency  to  put  too  much  crown  upon  the  macadam  surface.  This 
results  in  the  travel  being  confined  to  the  center  of  the  road,  because 
of  the  discomfort  experienced  in  driving  on  one  side.  Thus  the  center  of 
the  road  wears  much  more  rapidly  than  the  sides,  and  is  soon  rutted. 
Fig.  6 shows  the  United  States  object  lesson  road  near  Salem  where  the 
crown  does  not  exceed  one  half  inch  per  foot.  Note  the  fact  that  the 
view  shows  no  main  traveled  track  on  any  part  of  the  surfaced  road. 

Two  very  common  errors  in  the  construction  of  macadam  roads  are 
using  an  insufficient  amount  of  fine  material  or  rock  screenings  as  a 
binder,  and  in  not  using  water  in  sufficient  quantities  for  flushing  during 
the  rolling  process.  The  office  of  this  flushing  process  is  to  thoroughly  pud- 
dle the  mass  by  working  the  finer  particles  into  the  voids  and  thereby  bring- 
ing about  conditions  for  more  perfect  capillary  action.  (See  discussion  of 
cementing  value  of  rocks). 

These  are  vital  points  in  road  construction  and  no  road  builder  can  ignore 
them  and  succeed. 

COST  DATA. 

The  statistics  on  the  cost  of  general  road  construction  is  a variable 
quantity,  being  approximately  inversely  proportional  to  the  good  judg- 
ment and  management  of  the  road  engineer.  However,  some  cost  data 
of  roads  built  in  the  Willamette  Valley  will  be  of  interest. 

The  following  estimates  were  received  from  H.  B.  Chapman,  superin- 
tendent of  Multnomah  county,  showing  the  average  results  covering  125 
miles  of  macadam  road  built  in  that  county. 

Grading  averages  about  25  cents  per  yard.  With  the  average  prevailing 
conditions  in  Multnomah  County  this  would  mean  a cost  of  $500  to 
$750  per  mile. 

Cost  of  crushing  runs  from  25  cents  to  $1.25  per  cubic  yard.  This 
includes  stripping,  drilling  and  blasting.  The  number  of  yards  of 
crushed  rock  used  to  the  mile  on  a 16  foot  road  bed  6 inches  deep 
consolidated  is  2500  cubic  yards. 

Hauling  costs  about  25  cents  per  yard  mile.  Three  miles  being  the 
maximum  haul. 

Cost  of  preparing  the  road  bed  to  receive  the  rock  when  road  bed  is 
16  feet  wide,  6 to  8 inches  deep,  finished  macadam,  with  water  near  by 
for  flushing,  is  from  7 to  10  cents  per  square  yard  or  25  cents  per  cubic 
yard  of  rock  laid. 

Summary  of  Data  of  Multnomah  County. 


Clearing,  etc.,  per  mile $ 100  to  $ 500 

Grading 500  to  750 

Crushing  rock 1,875  to  3,750 

Hauling 625  to  1,875 


Total 


3,100  6,875 


PiyATE  14. — Germantown  road  near  Portland.  Showing  proju  r 1 


Plate  15. — Liberty  road,  Marion  County, 


58 


The  following  is  a specific  case  of  Marion  County’s  expense  in  road 
construction  as  taken  from  the  records  in  the  County  Clerk’s  Office. 
Expenses  incurred  in  building  a little  over  a mile  of  the  Turner  Road. 
A large  amount  of  volunteer  labor  was  performed,  no  account  of  which 
has  been  kept;  to  offset  this  some  five  miles  of  additional  road  bed  was 


prepared  at  the  same  time. 

Expense  of  moving  crusher  and  roller $ 26.73 

“ “ Engineers  at  rock  crusher  plant  279.25 

“ “ powder  35.10 

“ “ repairs  on  crusher  and  other  tools  162,30 

“ “ rock  bin  at  Turner  plant  136.33 

“ “ wood  used  by  the  crusher  and  roller 198.75 

“ “ lumber  used  at  Turner  crusher 32.54 

“ “ labor  on  Turner  road  2,071.00 

“ “ surveying  Turner  road  ' 53.45 

“ “ new  tools  9.55 

“ “ advertising  for  the  Turner  road  16.15 

“ “ moving  tools  to  county  shed  3.00 


Total  $3,030.17 

The  above  does  not  take  into  account  the  labor  that  was  furnished  by 
the  convicts  who  were  employed  to  do  a considerable  portion  of  the 
labor.  The  expense  of  the  convict  camp  is  as  follows: 

Provisions  for  the  Convict  Camp  $ 891.70 

Fixtures  for  the  Convict  Camp  38.90 

Bunk  house  138.40 

Guarding  convicts  725.70 

Tobacco  for  convicts  48.65 


Total  $1,843.43 


The  number  of  days  of  convict  labor  performed  were  given  as  1543.  If 
we  allow  nothing  for  the  wage  of  the  convict  labor  as  above,  the  cost 
of  the  finished  road  would  total  $4,873.69  per  mile. 

On  the  other  hand  if  we  allow  $2.50  per  day  for  the  1543  days  of  labor 
and  deduct  the  $1,943.43,  the  cost  of  feeding  and  guarding  the  convict 
camp  as  above,  the  total  mile  of  road  will  cost  about  $6,887.67.  The 
convict  labor  thereby  saving  the  county  about  $2,014.07  on  the  mile  of 
road  built. 

The  following  is  an  itemized  list  of  expenses  incurred  at  the  Sublimity 


rock  crushing  plant  for  the  year  1908: 

Expense  of  moving  crusher  from  Turner  to  Sublimity $ 76.00 

“ “ repairs  on  crusher  178.10 

“ “ new  tools  101.01 

“ “ tool  steel  41.70 

“ “ coal  10.40 

Miscellaneous  expense  at  the  plant 24.05 


59 


Nails  7.30 

Expense  of  iron  4.94 

“ “ repairs  on  tools  7.50 

“ “ oil  10.40 

“ “ powder  76.00 

“ “ labor  running  the  crusher  382.33 


Total  $919.71 

Expense  of  guarding  convicts  $ 427.5fc 

“ “ provisions  for  convict  camp  459.00 

“ “ tobacco  for  convict  camp  40.71 

“ “ cook  for  convict  camp  14.00 

“ “ fixtures  and  incidentals  for  for  the  camp  55.10 

“ “ clothing  for  convicts  1.30 


Total  $1,917.32 


Enough  rock  was  crushed  for  one  mile  of  road,  or  about  2000  cubic 
yards.  Approximate  number  of  days  of  convict  labor  performed  was 
about  1120,  for  which  the  state  was  paid  five  cents  per  day,  $56.00.  If 
we  deduct  the  cost  to  the  county  of  feeding  and  guarding  the  convicts 
and  allow  $2.50  per  day  for  the  1120  days  work  which  they  furnished  to 
the  county,  the  cost  of  the  rock  would  approach  or  approximate  $3719.71. 
This  approaches  the  maximum  cost  of  crushing  enough  rock  for  one 
mile  of  road  in  Multnomah  County. 

FREIGHT  RATES  ON  ROAD  MATERIAL. 

The  following  table  shows  the  rates  authorized  by  the  different 
railroad  companies  of  the  valley  for  the  hauling  of  sand,  gravel,  crushed 
rock  and  stone: 


5 miles  and  less 

2c 

per 

100 

lbs. 

Over  5 miles  and 

not  over  15 

mines 

3 c 

44 

100 

“ 

“ 15 

44 

44 

44 

“ 

25 

44 

3Y2C 

fee 

100 

“ 

" 25 

44 

44 

44 

“ 

35 

44 

4 c 

« 

100 

“ 

“ 35 

“ 

44 

44 

44 

45 

“ 

44 

100 

44 

“ 45 

(4 

44 

44 

44 

55 

“ 

5 c 

44 

100 

“ 

“ 55 

4€ 

44 

44 

44 

65 

44 

“ 

100 

44 

“ 65 

44 

44 

44 

44 

75 

44 

6 c 

44 

100 

“ 75 

44 

44 

44 

44 

85 

“ 

100 

“ 

“ 85 

“ 

44 

44 

44 

95 

44 

7 c 

44 

100 

“ 

“ 95 

44 

44 

“ 

44 

105 

“ 

7V2C 

100 

44 

The  above  rates  apply  on  car  load  lots  and  are  subject  to  a minimum 
rate  based  on  the  carrying  capacity  of  the  car  used.  Special  rates  are 
sometimes  quoted  to  counties. 


60 


SUMMARY  AND  CONCLUSION. 

In  the  preceding  pages  it  has  been  pointed  out  that  in  order  to  intelli- 
gently determine  the  value  of  a rock  for  road  material,  it  is  necessary 
to  understand  its  structure,  as  well  as  the  important  physical  properties 
of  its  constituent  minerals. 

It  has  also  been  shown  that  the  abrasion  test  for  determining  the 
percentage  of  wear,  is  by  far  the  most  important  mechanical  test,  and 
that  the  cementing  test  which  has  been  given  so  much  weight  by  some 
authorities  is  of  no  practical  value. 

It  has  also  been  shown  that  the  so-called  cementing  action  in  macadam 
roads  is  due  to  an  interwedging  effect  between  the  rock  particles,  and 
the  binding  power  is  due  to  capillarity  and  surface  tension  of  water. 

It  has  been  pointed  out  that  the  gravels  in  the  bed  of  the  Willamette 
river  are  most  fortunately  located  in  the  valley,  since  these  gravels  are 
excellent  material  and  can  be  dredged,  crushed  and  put  on  the  road 
with  much  less  expense  than  quarry  rock. 

It  has  been  shown  that  the  principles  of  rock  weathering  are  of  very 
great  importance  in  determining  the  value  of  rocks  as  road  metal,  and 
in  the  selection  of  quarry  sites. 

The  Willamette  valley  is  probably  better  supplied  with  excellent  road 
material  than  any  other  important  agricultural  district  of  equal  area  in 
the  country. 


GLOSSARY  OF  SCIENTIFIC  TERMS  USED  IN  THIS  BULLETIN. 


ACID. — Containing  a high  percentage  of  silica-bearing  minerals.  Op- 
posed to  basic. 

AEOLIAN. — Sediments  carried  and  deposited  by  the  action  of  the  wind. 

AMPHLBOLE. — See  Hornblende. 

ANDESITE. — A very  fine  grained  volcanic  rock  (lava)  consisting  when 
fresh  essentially  of  feldspar  and  pyroxene,  hornblende  or  dark 
colored  minerals. 

ARGILLACEOUS. — Originally  clayey  in  composition. 

BASIC. — Containing  a low  percentage  of  silica  and  a relatively  high 
percentage  of  lark-colored,  iron-bearing  minerals  (hornblende, 
pyroxenefi  etc.) 

BASALT. — A very  fine  grained  volcanic  rock  (lava),  dark  in  color,  con- 
sisting of  the  ferro-magnesian  minerals. 

CALCAREOUS. — Containing  calcite. 

CALCITE. — Carbonate  of  lime  (CaC03). 

CHERT. — A variety  of  silica. 

CHLORITE. — A greenish,  soft,  platy  mineral.  Chemically  a silicate  of 
aluminum  and  magnesium  (or  iron).  Often  a decomposition  product 
of  hornblende  or  pyroxene. 

CONGLOMERATE. — A rock  consisting  of  rounded  pebbles  or  boulders 
cemented  together. 

CRYSTALLINE. — Made  up  of  crystal  grains. 

CLEAVAGE. — The  breaking  of  a mineral  along  definite  plains  which  is 
due  to  geometrical  moleculor  arrangement. 

DIABASE. — A dark  colored  igneous  rock  consisting,  when  fresh,  mainly 
of  plagioclase  feldspar  and  pyroxene,  usually  with  some  magnetite 
(iron  oxide).  Normally  shows  a characteristic  interlocking  of 
crystal  grains. 

DOLAMITE. — A carbonate  of  magnesia  and  lime.  Resembles  limestone. 

DIORITE. — A granitic  igneous  rock  consisting,  when  fresh,  of  plagio- 
clase feldspar,  hornblende,  pyroxene  and  in  some  cases  with  a 
small  amount  of  quartz.  Usually  darker  in  color  than  the  granites. 

EXTRUSIVE. — Igneous  rocks  that  are  poured  out  on  the  surface  of  the 
earth  as  in  the  lava  flows. 

EROSION. — The  wearing  away  of  portions  of  a rock  mass  by  such 
natural  agencies  as  stream,  ice,  or  wave  action. 

FELDSPAR. — The  feldspars  are  silicates  of  aluminum  with  various 
amounts  of  potash,  soda,  and  lime.  Hard  minerals  with  good 
cleavage  in  two  directions.  Usually  white  to  pink  or  gray  in  color. 

FOLIATED. — A rock  which  is  made  up  of  parallel  groups  of  minerals 
such  as  mica. 

GABBRO. — A coarse  grained  crystalline  rock  composed,  when  fresh, 
mainly  of  plagioclase  feldspar  and  pyroxene.  Differs  from  diabase 
in  possessing  a granitic  rather  than  an  interlocking  or  diabasic 
structure. 

GNEISS. — A coarsely  foliated  or  laminated  rock. 


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GRANITE. — An  igneous  rock  usually  consisting,  when  fresh,  of  a crys- 
talline aggregate  of  quartz,  feldspar,  mica,  or  hornblende.  Usually 
gray  to  pinkish  in  color. 

GRANITIC. — Granite-like  in  composition  and  texture. 

HORNBLENDE. — A group  of  moderately  hard  minerals,  usually  dark 
green  to  black  in  color.  Silicates  of  lime,  magnesia,  iron,  and 
alumina.  A common  constituent  of  diorites  and  many  granites. 

IGNEOUS. — A term  applied  to  rocks  that  have  soldified  from  a molten 
condition. 

INTRUSIVE. — Rocks  that  have  been  forced  up  from  depths  into  the 
solid  crust  of  the  earth  while  in  a plastic,  heated  condition. 

JOINTS. — Rather  large  and  continuous  fracture  planes  in  rocks,  usually 
steeply  inclined. 

KAOLIN. — A variety  of  clay,  white  in  color.  Alteration  product  of 
feldspars. 

MAGNETITE. — Magnetic  iron  ore — iron  oxide;  hard,  metallic,  black, 
and  opaque. 

METAMORPHIC. — A term  applied  to  rocks  whose  constituents  have  been 
recrystallized  either  with  or  without  chemical  change  and  which 
have  been  subjected  at  some  time  to  heat  and  pressure. 

MARBLE. — Metamorphic  limestone. 

MICA. — Minerals  distinguishable  by  a very  easy  cleavage  whereby  they 
can  be  split  into  very  thin  elastic  leaves.  All  micas  are  silicates 
of  aluminum,  containing  alkalies,  with  oxides  of  iron  and  magnesium. 

MICRO-CRYSTALLINE. — Crystals  can  only  be  seen  under  the  micro- 
scope. 

ORTHOCLASE. — Potash  feldspar.  The  common  feldspar  of  granite. 

ORGANIC. — Being  formed  by  plant  or  animal  life  at  some  time. 

PLAGIOCLASE. — A name  applied  to  a group  of  feldspars  which  are 
silicates  of  alumina  and  soda  or  alumina  with  both  soda  and 
lime.  Often  distinguished  from  orthoclase  by  the  striations,  or  ap- 
parent scratches  on  the  cleavage  face. 

PORPHYRITIC.— Possessing  the  texture  of  a porphyry. 

PORPHYRY. — Any  rock  showing  crystals  embedded  in  a groundmass 
showing  much  finer  grain. 

PYROXENE. — Hard  minerals,  usually  dark  green  or  black  in  color. 
Silicates  of  magnesia  with  variable  proportions  of  iron,  lime,  and 
alumina.  Distinguishable  from  hornblende  by  cleavages  inter- 
secting approximately  at  right  angles  rather  than  at  an  acute  angle. 

PETROGRAPHIC. — From  the  study  of  a thin  section  under  the  micro- 
scope. 

QUARTZ. — Oxide  of  silicon,  Hard.  Usually  white  to  gray;  fractures 
irregularly;  a common  constituent  of  granites. 

QUARTZITES. — Rocks  that  were  originally  sandstones,  the  pores  having 
been  subsequently  filled  by  quartz  through  deposition  by  percolating 
waters.  A metamorphic  sandstone  very  often  forms  a quartzite. 


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RHYOLITE  — A type  of  extrusive  igneous  rock.  Having  the  same  miner- 
alogical  composition  as  the  granites  but  not  the  coarse  crystalline 
texture.  Usually  light  in  color. 

SANDSTONE. — A rock  originally  a sand,  but  subsequently  compacted 
and  the  grains  partially  cemented  together  so  as  to  form  a coherent 

rock. 

SCHIST. — A crystalline  rock  having  a foliated  or  parallel  structure  and 
splitting  easily  into  slabs  or  flakes,  less  uniform  than  in  slate. 

SECONDARY. — A term  applied  to  rock  minerals  which  are  derived 
partially  or  completely  from  the  alteration  of  other  minerals  in  the 
rock. 

SEDIMENTARY. — A term  applied  to  those  rocks  that  are  formed  by 
accumulations  derived  from  other  rocks  that  may  be  laid  down  by 
the  action  of  wind,  water,  or  by  chemical  precipitation. 

SHALE. — A bedded  rock  formed  by  the  consolidation  of  muds,  silits, 
or  clays. 

SILICA. — Oxide  of  silicon.  Quartz  is  the  commonest  form  of  silica. 

SILICEOUS. — Rich  in  silica  or  silica-bearing  minerals. 

SLATE. — An  argillaceous  rock  which  is  finely  laminated  and  fissile, 
either  due  to  very  easy  and  uniform  parting  along  bedding  planes 
or  (more  properly)  to  cleavage  planes  developed  as  a result  of 
compression  (as  in  roofing  slate.) 

SERPENTINE. — A soft  green  mineral  with  a greasy  feel.  A secondary 
mineral  formed  from  pyroxene  or  amhibole. 

SYENITE. — A granitic  rock  having  no  quartz. 

TRAP. — A general  term  for  igneous  rocks  of  the  dark  basic  type.  Such 
as  the  basalts  or  diabases. 

TRACHYTE. — A compact  igneous  rock  consisting,  when  fresh,  mainly 
of  potash  feldspar  in  small  lath-shaped  crystals,  with  various 
amounts  of  plagioclase,  biotite,  pyroxene,  and  hornblende. 

TALC. — An  alteration  product  of  pyroxene  and  amphibole.  Usually 
white  to  greenish  gray  in  color.  Closely  allied  to  Serpentine 
chemically.  A hydrogen  magnesium  silicate.  Has  a greasy  feel 
like  serpentine. 

TERTIARY. — One  of  the  recent  geological  epochs.  The  Tertiary  Period 
is  further  divided  into  the  Eocene,  Miocene,  Pliocene,  and  Pleistocene 
in  order  of  time. 

TUFF. — A volcanic  product  of  the  explosive  type.  Fine  mineral  aggre- 
gates that  accumulate  after  the  settling  of  the  volcanic  products 
blown  into  the  air. 

VOLCANICS. — A name  applied  to  igneous  rocks  which  have  been 
deposited  at  the  surface  of  the  earth  either  as  flows  of  lava  or  as 
bedded  masses  composed  largely  of  lava  fragments.  They  may  be 
acid  or  basic. 


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